U.S. patent application number 14/775581 was filed with the patent office on 2016-02-25 for electrical stimulation system with pulse control.
The applicant listed for this patent is MyndTec Inc.. Invention is credited to Arkadiusz BIEL, Richard FINE, Milos Radomir POPOVIC, Harold Max WODLINGER.
Application Number | 20160051817 14/775581 |
Document ID | / |
Family ID | 51535715 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160051817 |
Kind Code |
A1 |
POPOVIC; Milos Radomir ; et
al. |
February 25, 2016 |
Electrical Stimulation System with Pulse Control
Abstract
An electrical stimulation system to provide pulse stimulation to
an area of a living body by way of one or more electrode leads
applied to the area, the area including an associated resistance
element and an associated capacitance element. The system may
include a pulse generating circuit having a controllable output
voltage to generate constant voltage pulses to the one or more
electrode leads, wherein the corresponding current signal of each
constant voltage pulse includes an exponential decay to a steady
state current value. The system may include a controller configured
to estimate the associated resistance element of the area,
determine a specified target steady state current value to be
applied to the area, and control the pulse generating circuit to
generate a constant voltage pulse to the one or more electrode
leads at a calculated voltage level which achieves the specified
target steady state current value to the area.
Inventors: |
POPOVIC; Milos Radomir;
(Mississauga, CA) ; BIEL; Arkadiusz; (Toronto,
CA) ; WODLINGER; Harold Max; (Vaughan, CA) ;
FINE; Richard; (Mississauga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MyndTec Inc. |
Mississauga |
|
CA |
|
|
Family ID: |
51535715 |
Appl. No.: |
14/775581 |
Filed: |
March 13, 2014 |
PCT Filed: |
March 13, 2014 |
PCT NO: |
PCT/CA2014/050236 |
371 Date: |
September 11, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61791805 |
Mar 15, 2013 |
|
|
|
Current U.S.
Class: |
607/74 ;
607/72 |
Current CPC
Class: |
A61N 1/37247 20130101;
G06Q 50/22 20130101; G16H 20/30 20180101; G06Q 50/24 20130101; A61N
1/36034 20170801; A61N 1/36139 20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/372 20060101 A61N001/372 |
Claims
1. An electrical stimulation system for providing pulse stimulation
to an area of a living body by way of one or more electrode leads
applied to the area, the area including an associated resistance
element and an associated capacitance element, comprising: a pulse
generating circuit having a controllable output voltage to generate
constant voltage pulses to the one or more electrode leads, wherein
the corresponding current signal of each constant voltage pulse
includes a spike in current followed by an exponential decay to a
steady state current value; a controller configured to: estimate
the associated resistance element of the area, determine a
specified target steady state current value to be applied to the
area, and control the pulse generating circuit to generate a
constant voltage pulse to the one or more electrode leads at a
calculated voltage level which achieves the specified target steady
state current value to the area, wherein each generated constant
voltage pulse has a faster rise time resulting in a lower required
specified target steady state current than when compared to a
rectangular constant current pulse or a constant voltage pulse
having a slower rise time requiring a higher required specified
target steady state current, less energy supply is required to
provide the lower required specified target steady state
current.
2. (canceled)
3. The electrical stimulation system as claimed in claim 1, wherein
the calculated voltage level is calculated without consideration of
a value of the associated capacitance element.
4. The electrical stimulation system as claimed in claim 1, wherein
the controller is further configured to determine the associated
resistance element of the area.
5. The electrical stimulation system as claimed in claim 1, further
comprising a signal detector configured to detect signal parameters
associated with the area of the living body, wherein the associated
resistance element is determined from at least the detected signal
parameters.
6. The electrical stimulation system as claimed in claim 4, wherein
the controller is further configured to initially estimate the
associated resistance element by applying one or more sub-threshold
pulses to the area from the pulse generating circuit.
7. The electrical stimulation system as claimed in claim 1, wherein
said estimating of the associated resistance element is performed
by measuring the steady-state current during at least one of the
pulses.
8. The electrical stimulation system as claimed in claim 1, wherein
said determining the specified target steady state current value
includes receiving the specified target steady state current value
from a computer device, a user interface device, or from a
memory.
9.-11. (canceled)
12. The electrical stimulation system as claimed in claim 1,
wherein the controller is further configured to: determine a next
specified target steady state current value to be applied to the
area; and control the pulse generating circuit to generate a next
constant voltage pulse to the one or more electrode leads at a next
calculated voltage level which achieves the next specified target
steady state current value to the area.
13. The electrical stimulation system as claimed in claim 12,
wherein the next calculated voltage level is calculated based on
consideration of any determined changes to the associated
resistance element of the area.
14. The electrical stimulation system as claimed in claim 1,
wherein the constant voltage pulses provide sequential bipolar
pulse stimulation comprising a pulse sequence including a positive
constant voltage pulse and a negative constant voltage pulse
through the area by way of the one or more electrode leads.
15. The electrical stimulation system as claimed in claim 14,
wherein an amplitude and pulse width of the positive pulse and the
negative pulse are controlled to be charge balanced during the
pulse sequence.
16.-19. (canceled)
20. The electrical stimulation system as claimed in claim 1,
wherein a rise time of the spike in current is predominantly
dictated by a switching speed of switches.
21. The electrical stimulation system as claimed in claim 1,
further comprising a selectively activatable signal path from the
switching circuit which is an alternate signal path from the area
to selectively discharge any charge from the substantially constant
voltage supply between pulses.
22. The electrical stimulation system as claimed in claim 1,
wherein the electrical stimulation system comprises a functional
electrical stimulation system.
23.-24. (canceled)
25. The electrical stimulation system as claimed in claim 1,
further comprising a plurality of pulse generating circuits
including the pulse generating circuit, a plurality of electrodes
including the one or more electrode leads, wherein the electrode
leads are each applied to a respective plurality of areas including
the area, wherein at least two of the plurality of areas are of a
distance which causes biological cross-talk between respective
electrode leads, wherein the controller is further configured to
control the spike of one of the current signals for one of the
electrode leads so as to be outside the steady-state current of
another one of the electrode leads so as to allow accurate
measurement of the steady-state current of the another one of the
electrode leads.
26. The electrical stimulation system as claimed in claim 25,
wherein each constant voltage pulse of each of the electrode leads
are all activated substantially simultaneously.
27. A method for controlling an electrical stimulation system for
providing pulse stimulation to an area of a living body by way of
one or more electrode leads applied to the area, the area including
an associated resistance element and an associated capacitance
element, wherein the electrical stimulation system includes a pulse
generating circuit having a controllable output voltage to generate
constant voltage pulses to the one or more electrode leads, wherein
the corresponding current signal of each constant voltage pulse
includes a spike in current followed by an exponential decay to a
steady state current value, the method comprising: estimating the
associated resistance element of the area; determining a specified
target steady state current value to be applied to the area; and
controlling the pulse generating circuit to generate a constant
voltage pulse to the one or more electrode leads at a calculated
voltage level which achieves the specified target steady state
current value to the area, wherein each generated constant voltage
pulse has a faster rise time resulting in a lower required
specified target steady state current than when compared to a
rectangular constant current pulse or a constant voltage pulse
having a slower rise time requiring a higher required specified
target steady state current, wherein less energy supply is required
to provide the lower required specified target steady state
current.
28. A controller for controlling an electrical stimulation system
for providing pulse stimulation to an area of a living body by way
of one or more electrode leads applied to the area, the area
including an associated resistance element and an associated
capacitance element, wherein the electrical stimulation system
includes a pulse generating circuit having a controllable output
voltage to generate constant voltage pulses to the one or more
electrode leads, wherein the corresponding current signal of each
constant voltage pulse includes a spike in current followed by an
exponential decay to a steady state current value, the controller
being configured to: estimate the associated resistance element of
the area; determine a specified target steady state current value
to be applied to the area; and control the pulse generating circuit
to generate a constant voltage pulse to the one or more electrode
leads at a calculated voltage level which achieves the specified
target steady state current value to the area, wherein each
generated constant voltage pulse has a faster rise time resulting
in a lower required specified target steady state current than when
compared to a rectangular constant current pulse or a constant
voltage pulse having a slower rise time requiring a higher required
specified target steady state current, wherein less energy supply
is required to provide the lower required specified target steady
state current.
29.-36. (canceled)
37. An electrical stimulation system for providing pulse
stimulation to a plurality of areas of a living body by way of a
plurality of electrode leads each applied to one of the respective
areas, each of the areas including an associated resistance element
and an associated capacitance element, at least two of the
plurality of areas are of a distance which causes biological
cross-talk between respective electrode leads, the system
comprising: a plurality of pulse generating circuits each having a
controllable output voltage to generate constant voltage pulses to
one or more of the electrode leads, wherein the corresponding
current signal of each constant voltage pulse includes an
exponential decay to a steady state current value; and at least one
controller is configured to: estimate the associated resistance
element of each area, control the pulse generating circuits to
generate a constant voltage pulse to each of the electrode leads at
a specified voltage level based on the measured steady-state
current value, and control a spike of one of the current signals
for one of the electrode leads so as to be outside the steady-state
current of another one of the electrode leads to allow accurate
measurement of the steady-state current of the another one of the
electrode leads.
38. The electrical stimulation system as claimed in claim 1,
wherein each constant voltage pulse has a rise time of 50
nanoseconds or less.
39. The electrical stimulation system as claimed in claim 1,
wherein each constant voltage pulse has a rise time of 20
nanoseconds or less.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Patent Application No. 61/791,805 filed Mar. 15, 2013, the contents
of which are herein incorporated by reference.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to electrical stimulation,
and for example, to a functional electrical stimulation device and
system.
BACKGROUND
[0003] The general principles of functional electrical stimulation
(FES) are rooted in the physiological process of nerve and muscle
excitation. These excitations are a result of action potentials
(APs) that occur in the body at the neuronal and muscular levels.
APs are the messenger signals for the neuromuscular system. They
occur in muscle and nervous system tissues in response to stimuli,
which can be natural or artificial. In the case of FES, these
stimuli are charge pulses. Depending on the amplitude, duration and
frequency of these stimuli they can cause excitation in different
tissues. FES therapies use these excitation pulses to treat
patients with impairments in different areas of the body. Owing to
the complexity of generating APs, the artificial electrical
stimulation pulses which can generate these APs may require
particular pulse types and stimulation schemes for FES
applications.
[0004] All body cells display a membrane potential, which is a
separation of positive and negative charges across the membrane.
This potential is related to the uneven distribution of potassium
ions (K+ ions), sodium ions (Na+ ions) and large intracellular
protein anions between the intracellular and extracellular fluid
and to the differential permeability of the plasma membrane to
these ions and to activate ion pump mechanisms.
[0005] Two types of cells, muscle cells and nerve cells, have
developed specialized use for this membrane potential. Nerve and
muscle are excitable tissues that produce action potentials when
their resting potentials change through excitation or other
biological processes. Action potentials allow nerve and muscle
cells to communicate. FES uses artificial stimuli in the form of
electrical pulses to elicit excitation in different tissues.
[0006] Neuromuscular electrical stimulation (NMES) is one of the
useful therapeutic methods to improve motor function. Studies
examining the use of NMES have demonstrated improvements in joint
range of motion, force and torque production, magnitude of
electromyographic (EMG) muscular activity, and muscle tone.
Functional electrical stimulation (FES) is a device-mediated
therapy that integrates electrical stimulation of sensory-motor
systems and repetitive functional movement of the paretic limb or a
body part or a body function in patients with different forms of
neuromuscular disorder, such as stroke, spinal cord injury,
multiple sclerosis, cerebral palsy, and traumatic brain injury, to
name a few.
[0007] Some known FES devices, although useful, have had limited
success at reaching their full potential. For example, some
previous devices have not been able to ensure charge balance over
time because of partial control over temporal characteristics and
amplitude. They also provide a limited number of pulses and require
complicated and costly adjustments for use in different FES
applications.
[0008] Nonetheless, various functional electrical stimulators have
been used over time to improve the lives of patients with various
neurological and musculoskeletal disorders and muscular atrophies
as well as in therapy for sport injuries. Known FES devices provide
electrical pulses activating a single or a group of muscles, to
create a movement (neuroprosthetic applications) and/or build up
the muscle mass (neuromuscular stimulation applications). FES
devices have also been used in treating bladder problems, easing
the symptoms of Parkinson's disease and numerous other
applications. Generally, for each application a specific FES system
is used.
[0009] Some existing known stimulators typically produce either
voltage or current regulated electrical pulses. Current regulated
pulses generally deliver the same amount of charge to the tissue
regardless of tissue resistance. However, some existing systems,
which regulate current, have very slow voltage rise times, which
can lead to high steady state current, leading to discomfort.
[0010] Other difficulties may be appreciated in view of the
detailed description below.
SUMMARY
[0011] It is recognized herein that stimulating with a very fast
voltage rise time (e.g. 10 to 20 ns) results in significantly less
steady-state current required to achieve the same stimulation. It
is recognized herein that a fast rise time may assist to reduce the
stimulation intensity applied to the patient.
[0012] At least some example embodiments relate to a functional
electrical stimulation (FES) system and associated methods. The
system provides pulse stimulation to an area of a living body by
way of one or more electrode leads applied to the area, the area
including an associated resistance element and an associated
capacitance element. The system may include a pulse generating
circuit having a controllable output voltage to generate constant
voltage pulses to the one or more electrode leads, wherein the
corresponding current signal of each constant voltage pulse
includes an exponential decay to a steady state current value. The
system includes a controller configured to estimate the associated
resistance element of the area, determine a specified target steady
state current value to be applied to the area, and control the
pulse generating circuit to generate a constant voltage pulse to
the one or more electrode leads at a calculated voltage level which
achieves the specified target steady state current value to the
area.
[0013] In accordance with an example embodiment, there is provided
a method for controlling an electrical stimulation system for
providing pulse stimulation to an area of a living body by way of
one or more electrode leads applied to the area, the area including
an associated resistance element and an associated capacitance
element, wherein the electrical stimulation system includes a pulse
generating circuit having a controllable output voltage to generate
constant voltage pulses to the one or more electrode leads, wherein
the corresponding current signal of each constant voltage pulse
includes an exponential decay to a steady state current value. The
method includes estimating the associated resistance element of the
area, determining a specified target steady state current value to
be applied to the area, and controlling the pulse generating
circuit to generate a constant voltage pulse to the one or more
electrode leads at a calculated voltage level which achieves the
specified target steady state current value to the area.
[0014] In accordance with another example embodiment, there is
provided a controller for controlling an electrical stimulation
system for providing pulse stimulation to an area of a living body
by way of one or more electrode leads applied to the area, the area
including an associated resistance element and an associated
capacitance element, wherein the electrical stimulation system
includes a pulse generating circuit having a controllable output
voltage to generate constant voltage pulses to the one or more
electrode leads, wherein the corresponding current signal of each
constant voltage pulse includes an exponential decay to a steady
state current value. The controller is configured to estimate the
associated resistance element of the area, determine a specified
target steady state current value to be applied to the area, and
control the pulse generating circuit to generate a constant voltage
pulse to the one or more electrode leads at a calculated voltage
level which achieves the specified target steady state current
value to the area.
[0015] In accordance with yet another example embodiment, there is
provided a non-transitory computer readable medium having
instructions stored thereon executable by a controller for
controlling an electrical stimulation system for providing pulse
stimulation to an area of a living body by way of one or more
electrode leads applied to the area, the area including an
associated resistance element and an associated capacitance
element, wherein the electrical stimulation system includes a pulse
generating circuit having a controllable output voltage to generate
constant voltage pulses to the one or more electrode leads, wherein
the corresponding current signal of each constant voltage pulse
includes an exponential decay to a steady state current value. The
instructions include instructions for estimating the associated
resistance element of the area, determining a specified target
steady state current value to be applied to the area, and
instructions for controlling the pulse generating circuit to
generate a constant voltage pulse to the one or more electrode
leads at a calculated voltage level which achieves the specified
target steady state current value to the area.
[0016] In accordance with yet another example embodiment, there is
provided a tablet computer for controlling a processor board which
provides pulse stimulation to an area of a living body by way of
one or more electrode leads applied to the area, the area including
an associated resistance element and an associated capacitance
element, wherein the processor board controls a pulse generating
circuit having a controllable output voltage to generate constant
voltage pulses to the area, wherein the corresponding current
signal of each constant voltage pulse includes an exponential decay
to a steady state current value, The tablet computer includes: a
touchscreen for displaying a user interface which at least displays
an option to activate the pulse generating circuit; and a
controller configured to estimate the associated resistance element
of the area, determine a specified target steady state current
value to be applied to the area, and control the pulse generating
circuit, through the processor board, to generate a constant
voltage pulse to the one or more electrode leads at a calculated
voltage level which achieves the specified target steady state
current value to the area.
[0017] In accordance with yet another example embodiment, there is
provided a computer device for managing patient information in
relation to electrical stimulation therapy by way of pulses applied
to a patient, the device including: an interface for receiving
information in relation to the electrical stimulation therapy, the
information including detected information of the pulses applied to
the patient; a memory for storing the received information; and a
communications subsystem for communicating the received information
to a remote server.
[0018] In accordance with yet another example embodiment, there is
provided a method of prescribing a treatment to a patient,
including: receiving a prescription purchase request; and providing
a patient dedicated electronic key in response to the purchase
request, wherein the electronic key comprises at least one or all
of: a. access to protocol(s) for a prescribed therapy intervention,
b. a record of the pattern of use of the protocols, including at
least duration, frequency and amplitude of pulses to be applied to
the patient, c. outcomes captured during treatment, and d. reports
on progress and treatment planning.
[0019] In accordance with yet another example embodiment, there is
provided a computer device for controlling an electrical
stimulation system for providing pulse stimulation to a patient,
including: a display screen which displays a graphical user
interface (GUI), the GUI being configured to receive user inputs in
relation to the pulse stimulation for at least one of: a.
protocols, b. diagnostics that report patient progress, and c.
instructional material including videos, help menus or user
manual.
[0020] In accordance with yet another example embodiment, there is
provided an electrical stimulation system for providing pulse
stimulation to a plurality of areas of a living body by way of a
plurality of electrode leads each applied to one of the respective
areas, each of the areas including an associated resistance element
and an associated capacitance element, at least two of the
plurality of areas are of a distance which causes biological
cross-talk between respective electrode leads, the system
including: a plurality of pulse generating circuits each having a
controllable output voltage to generate constant voltage pulses to
one or more of the electrode leads, wherein the corresponding
current signal of each constant voltage pulse includes an
exponential decay to a steady state current value; and at least one
controller is configured to: estimate the associated resistance
element of each area, control the pulse generating circuits to
generate a constant voltage pulse to each of the electrode leads at
a specified voltage level based on the measured steady-state
current value, and control a spike of one of the current signals
for one of the electrode leads so as to be outside the steady-state
current of another one of the electrode leads to allow accurate
measurement of the steady-state current of the another one of the
electrode leads.
[0021] Other aims, objects, advantages and features of the example
embodiments, and/or difficulties with existing conventional
systems, will become more apparent upon reading of the following
non-restrictive description of specific embodiments thereof, given
by way of example only with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0022] Example embodiments of the present disclosure will be
provided, by way of examples only, with reference to the appended
drawings, in which:
[0023] FIG. 1 is a schematic representation of various pulse
characteristics applicable in different FES applications, a
selection of one or more of which being available through
implementation of different example embodiments;
[0024] FIG. 2 is a high level diagram of a FES system, in
accordance with one example embodiment;
[0025] FIG. 3 is a schematic diagram of an output stage of a FES
system, in accordance with one example embodiment;
[0026] FIG. 4 is a high level diagram of a FES system, in
accordance with another example embodiment;
[0027] FIG. 5 is a schematic diagram of the FES system of FIG. 4,
in accordance with an example embodiment;
[0028] FIGS. 6A, 6B, 6C and 6D (hereinafter each or collectively
referred to as "FIG. 6") illustrate a detailed schematic diagram of
one output stage of a FES system, in accordance with an example
embodiment;
[0029] FIG. 7 is an example schematic representation of an
equivalent circuit model for skin impedance of a patient, to which
example embodiments can be applied;
[0030] FIG. 8 illustrates a plot and schematic diagram of a signal
pulse applied to the patient, in accordance with an example
embodiment;
[0031] FIG. 9 is a plot of an asymmetrical pulse sequence applied
the patient, in accordance with an example embodiment;
[0032] FIG. 10 is a plot which illustrates the asymmetrical pulse
sequence of FIG. 9 as a pulse train, in accordance with an example
embodiment;
[0033] FIG. 11 is a plot of a symmetrical pulse sequence applied to
the patient, in accordance with an example embodiment;
[0034] FIG. 12 is a plot which illustrates the symmetrical pulse
sequence of FIG. 11 as a pulse train, in accordance with an example
embodiment;
[0035] FIG. 13 illustrates a flow diagram of an exemplary method
for applying signal pulses to the patient, in accordance with an
example embodiment;
[0036] FIG. 14 illustrates a flow diagram of another exemplary
method for applying signal pulses to the patient, in accordance
with another example embodiment;
[0037] FIG. 15 is a schematic picture of functional motion tasks
conducted, and of shoulder and elbow joint angle changes and
stimulus pattern of each muscle where thick and thin lines indicate
joint motion and stimulus pattern (timing of ON/OFF);
[0038] FIG. 16 is a schematic depiction of electrode locations;
[0039] FIG. 17 is a graph of recruitment curves of H-reflex and M
wave obtained in pre-training and at various time points;
[0040] FIG. 18 is a graph of exemplary elicited M wave and H-reflex
curves;
[0041] FIG. 19 is a graph of changes of H-reflex and M response
curves with time course of training;
[0042] FIG. 20 is a graph of a time course showing changes of a
maximal voluntary contraction level of the first distal
interosseous muscles (FDI), flexor capi radialis (FCR), extensor
digitorum (EDL), biceps brachialis (BB), triceps brachialis (TB),
anterior (aDel) and posterior deltoid (pDel) muscles compared to
the unaffected side arm as a reference;
[0043] FIG. 21 is an exemplary x-y plot of the absolute positions
of the shoulder, elbow, wrist joint, and index finger position
during a circle drawing test;
[0044] FIG. 22 is an exemplary x-y plot of the positions of the
elbow, wrist joint, and index finger position during a circle
drawing test normalized to the shoulder position;
[0045] FIG. 23 is an example high level diagram of a communication
system for one or more FES systems, in accordance with an example
embodiment;
[0046] FIG. 24 is an example flow diagram of user interface screens
on a computer device for controlling and managing an FES system, in
accordance with an example embodiment;
[0047] FIG. 25 is an example user interface screen displayed on a
computer device for patient treatment, in accordance with an
example embodiment;
[0048] FIG. 26 is an example user interface screen displayed on a
computer device for session details, in accordance with an example
embodiment;
[0049] FIG. 27 is an example user interface screen displayed on a
computer device for protocol details, in accordance with an example
embodiment;
[0050] FIG. 28 is an example user interface screen displayed on a
computer device for protocol setup, in accordance with an example
embodiment;
[0051] FIG. 29 is an example user interface screen displayed on a
computer device for channel setup, in accordance with an example
embodiment;
[0052] FIG. 30 is an example user interface screen displayed on a
computer device for administer protocol, in accordance with an
example embodiment; and
[0053] FIG. 31 is an example user interface screen displayed on a
computer device for session end, in accordance with an example
embodiment.
[0054] Like reference numerals may be used throughout the Figures
to denote similar elements and features.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0055] With reference to the disclosure herein and the appended
figures, a functional electrical stimulation (FES) device and
system, and use thereof will now be described, in accordance with
different example embodiments.
[0056] FIG. 1 shows common classifications of pulse shapes that can
be used in FES applications. A monopolar or unipolar pulse sequence
102 includes pulses from a reference state such as ground to and
from a positive state only, as shown, or alternatively a negative
state only. A bipolar pulse sequence 104 includes pulses which are
both positive and negative from the reference state. A symmetric
pulse sequence 106 includes consecutive pulses which have equal and
opposite amplitudes. An asymmetric pulse sequence 108 includes
consecutive pulses which may have unequal opposite amplitudes. The
pulse shapes can represent voltage or current, depending on the
particular application. A parameter of interest in FES
applications, particularly where bipolar pulses are used, is that
the net electric charge brought by each pulse be as close to zero
as possible, which parameter generally applies in the application
of symmetric and asymmetric bipolar pulses. This feature is
generally considered relevant in preventing or at least reducing
charge accumulation in the tissue, which may cause a galvanic
process that may lead to tissue breakdown, for example.
[0057] Reference is now made to FIG. 7, which is an example
schematic representation of an equivalent circuit model 700 for
impedance of an area or region of a patient 700 such as the skin,
to which example embodiments can be applied. The area of the
patient 700 can be represented by at least an associated resistance
element and an associated capacitance element. In the example
shown, the equivalent circuit model 700 includes a series
resistance (Rs) and, in parallel, a capacitor (Cp) and a resistor
(Rp). Other more complex models may be used in other example
embodiments, which may include further resistance elements and/or
further capacitance elements. For example, the electrode interface,
skin, spreading resistance, and body resistance, may further add
resistance elements and capacitance elements, as understood in the
art, which may be used depending on the desired model complexity.
The resistance elements and the capacitance elements of the patient
can change over time, for example based on physiological changes or
as a response to the present FES treatment (which can be e.g. 5
seconds). For example, note that skin characteristics of resistance
and capacitance can be significantly affected by variable factors
such as moisturizers. For the model 700, the associated total
resistance of the patient area can be represented by, for example,
Rs+Rp.
[0058] By measuring patient's skin resistance at different skin
points (where the stimulation is delivered), example embodiments of
the present FES systems can be used to create patients "resistance
signature". For example, this means that if somebody tries to use
the protocols assigned to subject A we can determine when somebody
tried to apply it to subject B. The patient's skin "resistance
signature" and the stimulation amplitudes (e.g. change in the
amplitudes coupled with different "resistance signature") can be
used to determine fraud or an attempt to use protocols assigned for
one person (person A) with another person (person B).
[0059] An example controlled pulse is best illustrated in FIG. 8,
which shows a plot 800 and associated schematic diagram of a signal
pulse applied to the patient 804, in accordance with an example
embodiment. The patient 804 may have a steady state resistance
value of 600 Ohms, for example. Generally, in accordance with at
least some example embodiments, there is provided a functional
electrical stimulation (FES) system 802 for providing pulse
stimulation to an area of the patient 804 by way of one or more
electrode leads applied to the area. The FES system 802 includes a
pulse generating circuit 820 having a controllable output voltage
to generate rectangular or near-rectangular constant voltage pulses
806 to the one or more electrodes. The rising edge of the voltage
pulses 806 have a high slew rate. Because the capacitance element
of the patient area (e.g. as illustrated FIG. 7) can be relatively
large, the corresponding current signal profile 808 of each
constant voltage pulse 806 includes an initial inrush of current
810 having a high slew rate, which then achieves a peak or spike
812. The spike 812 is followed by an exponential decay 814 to a
steady state current value 816. This type of current response can
also be referred to as a voltage step response, for example. The
system 802 can receive instructions or input from a practitioner
regarding the specified target steady state current value 816 to be
applied to the area, which is the desired charge dosage to the
patient 804. The voltage of the constant voltage pulse 806 is a
calculated voltage level which achieves the specified target steady
state current value to the area. For example, Ohms' Law (V=R*I) can
be used to calculate the required voltage level, dependent on the
present resistance element of the patient area 804 and the
specified target steady state current value. The present resistance
element of the patient 804 can be determined in a number of ways,
in accordance with example embodiments, as described in detail
herein.
[0060] For each subsequent pulse, the calculated constant voltage
level of the voltage pulse 806 is adjusted to achieve the specified
target steady state current (due to possible changes in patient
resistance element). This voltage adjustment is made by measuring
the current that is actually delivered by the target voltage,
determining the present electrical resistance element, and then
adjusting the target voltage level. The practitioner or user
specifies the stimulation in terms of steady state current, so that
the system delivers a consistent desired charge regardless of the
resistance element of the patient.
[0061] Accordingly, for each pulse the voltage is regulated to a
voltage level defined by a specified target steady-state current of
the patient 804, so that switch activation of each pulse provides
an initial inrush of current at the voltage level, and wherein the
resultant current achieves the specified target steady-state
current value. It is recognized herein that stimulating with a very
fast voltage rise time (e.g. 10 to 20 ns) results in significantly
less steady-state current required to achieve the same stimulation.
Note that, the example embodiments use constant voltage pulses
which are in contrast to, and not the same as, a pulse generator
which merely generates a rectangular constant current pulse.
[0062] In the example circuit 820 shown in FIG. 8, the pulse
generating circuit 820 can include at least a controllable constant
voltage source 822 and a switching circuit 824 which includes, for
example, switches in an H-bridge configuration. An alternate path
826 is also shown, which allows selective drainage of charge which
is alternate from the switching circuit 824.
[0063] Reference is now made to FIGS. 9 and 10, which illustrate a
plot of an asymmetrical pulse sequence 900 applied to the patient,
in accordance with an example embodiment. FIG. 10 is the pulse
sequence 900 applied as a pulse train having a specified frequency.
In an example embodiment, the illustrated pulse sequences are a
result of the one or more cathodes being places on the stimulation
target site(s) on the body, while the anode is placed at another
suitable site to complete a nerve stimulation path. In the examples
shown, each pulse sequence can include a negative pulse followed by
a positive pulse, wherein the positive pulse is one quarter of the
amplitude of the negative pulse, and has a pulse width that is four
times that of the negative pulse. This allows the charge across the
patient area to be balanced. Other example asymmetric pulses may
have different amplitude and pulse width ratios, wherein net charge
is balanced (e.g. equal or close to zero).
[0064] Referring to FIG. 9, the asymmetrical pulse sequence 900
illustrates the current pulse sequence 902 and the voltage pulse
sequence 904 as applied to the patient. At the negative pulse of
the voltage pulse sequence 904, the voltage applied is set to a
constant negative voltage level 906 (e.g. -V). The voltage level
906 is calculated in dependence of the desired target steady state
current value and the presently known value of the resistance
element of the patient. At the positive pulse of the voltage pulse
sequence 904, the voltage is applied as a constant positive voltage
level 908 which is one quarter of the negative voltage level (e.g.
1/4V) and four times the pulse width of the negative pulse.
[0065] At the negative pulse of the current sequence 902, the
current pulse includes an initial inrush of current 910 having a
high slew rate, which then achieves a peak or spike 912. The spike
912 is followed by an exponential decay 914 to a steady state
current value 916. Typically, the practitioner defines the
parameters of the desired pulse sequence 902 by specifying the
target steady state current value 916, and the voltage level 906 is
controlled to achieve that steady state current value 916.
[0066] At the positive pulse of the current sequence 902, the
current pulse includes an inrush of current 920 having a high slew
rate, which then achieves a peak or spike 922. The spike 922 is
followed by an exponential decay 924 to a steady state current
924.
[0067] Reference is now made to FIGS. 11 and 12, which illustrate a
plot of a symmetrical pulse sequence 1100 applied to the patient,
in accordance with an example embodiment. FIG. 12 is the pulse
sequence 1100 applied as a pulse train having a specified
frequency. For example, the illustrated pulse sequences are a
result of the one or more cathodes being places on the stimulation
target site(s) on the body, while the anode is placed at another
suitable site to complete a nerve stimulation path. In the example
shown, each pulse sequence can include a negative pulse and a
positive pulse which have equal and opposite amplitudes, and which
have equal pulse widths. This allows the charge across the patient
area to be balanced.
[0068] Referring to FIG. 11, the asymmetrical pulse sequence 1100
illustrates the current pulse sequence 1102 and the voltage pulse
sequence 1104 as applied to the patient. At the negative pulse of
the voltage pulse sequence 1104, the voltage applied is set to a
constant negative voltage level 1106 (e.g. -V). The voltage level
1106 is calculated in dependence of the desired target steady state
current value and the presently known value of the resistance
element of the patient. At the positive pulse of the voltage pulse
sequence 1104, the voltage is applied as a constant positive
voltage level 1108 having the same amplitude as the negative
voltage level (e.g. +V).
[0069] At the negative pulse of the current sequence 1102,
referring still to FIG. 11, the current pulse includes an initial
inrush of current 1110 having a high slew rate, which then achieves
a peak or spike 1112. The spike 1112 is followed by an exponential
decay 1114 to a steady state current value 1116. Typically, the
practitioner defines the parameters of the desired pulse sequence
1102 by specifying the target steady state current value 1116, and
the voltage level 1106 is controlled by the processor 408 (FIG. 4)
to achieve that steady state current value 1116.
[0070] At the positive pulse of the current sequence 1102,
referring still to FIG. 11, the current pulse includes an inrush of
current 1120 having a high slew rate, which then achieves a peak or
spike 1122. The spike 1122 is followed by an exponential decay 1124
to a steady state current 1124.
[0071] Reference is now made to FIG. 2, which provides a high level
diagram of an FES system 200, in accordance with one example
embodiment. In this particular embodiment, the FES system 200
consists of an external system, however, in some example
embodiments, a similar system may be designed and implemented for
internal implementation (e.g. at least some of the elements as an
implantable system). The system 200 generally comprises an output
stage 202 comprising a power stage 204 for creating electrical
pulses and a controller 206 that regulates operation of the power
stage 204. The system 200 may further include, or be configured
for, operative coupling with one or more stimulation electrodes 208
to deliver the pulses generated by the power stage 204 to the
targeted tissues, for example, through the skin (e.g.
surface/transcutaneous electrodes), directly by penetrating the
body (e.g. percutaneous electrodes), the electrodes are directly
implanted into the body, at least some other parts such as a
portable power source (e.g. 304 in FIG. 3) is also implanted into
the body, and/or at least some or all of the FES system 200 is
implanted into the body, and the like. A controller, for example a
central processing platform or central logic 210 is also
illustratively provided to communicate intended pulse
characteristics to the output stage 202, for example, external
inputs from a practitioner or operator user interface 214 (e.g. via
one or more activation switches, dials, footswitch(es),
handswitch(es), and/or other such user operable interfaces, and/or
via one or more user-selectable preprogrammed stimulation sequences
stored or otherwise accessed by the system for implementation) or
from another device, such as one or more physiological sensors 212
configured to regulate or influence operation of the FES system 200
based on one or more sensed physiological parameters. Example
biological signals that that may be used to drive the FES system
200 can include, for example, EMG signals, brain signals, EEG, ECoG
and others. Example embodiments can be applied to user interactions
protocols which use such signals. For example, 4 channels of EMG
may be used to assist in controlling the pulse delivery. These
sensed physiological parameters may be associated with or
indicative as to an effectiveness of the FES treatment in question,
for example. Other control feedback sensors or detectors may also
be considered by the central processing platform or central logic
210.
[0072] The structure of FES pulses for stimulation may be
determined by several characteristics, for example: pulse type
(current or voltage), amplitude, duration, rise time, frequency,
polarity, number of phases and symmetry, which characteristics will
be further described below.
[0073] Pulse type: As noted above, the provision of current
regulated pulses allows the desired charge to be controlled.
Inter-variable and intra-variable differences in tissue resistance
that may affect such pulses may include, but are not limited to,
perspiration, skin movement and increased circulation that
typically result from FES, for example. In some exemplary
embodiments of FES therapy, current regulation may be preferred
since a desired charge is delivered to the tissue, regardless of
the tissue resistance.
[0074] Pulse amplitude and duration: In general, an action
potential is only generated if the membrane potential reaches a
threshold membrane potential. From patient to patient, there is a
range of different tissue impedances. Also, within each patient,
each type of tissue may have distinct impedance. Therefore,
different currents of FES generated pulses may be necessary to
address these impedance variations. Also, the type of tissue being
stimulated may thus become a parameter for determining the
amplitude level and the pulse duration of a given FES treatment.
For example, localized stimulation of small muscles generally
requires shorter less intense pulses, whereas deeper muscle
stimulation requires higher amplitude and longer pulse
duration.
[0075] Pulse rise time: The rise time of current pulses may be
relevant in providing enhanced FES treatments. For example, if the
pulse rise time is too slow, the membrane potential may accommodate
or adjust to the stimulus. Accordingly, despite otherwise adequate
stimulation pulses, a threshold membrane potential may not be
achieved and the desired neuro-muscular excitation may not occur.
Similarly, an improved (i.e. decreased) pulse rise-time may
translate in lower requirements for pulse amplitude to achieve a
similar stimulation. Such reductions in pulse amplitude may
translate in a reduction in power consumption and a reduction in
the total absolute charge being applied to the tissue, which may be
of particular interest in certain applications.
[0076] Pulse frequency: The frequency of pulse delivery determines
the rate of action potential generation in the tissue. If the
stimulation frequency is at or greater than 40 Hz, the generated
action potentials create continuous muscle (tetanic) contractions.
If the stimulation frequency is between 16 and 40 Hz, many
individuals may feel discontinuous muscle contraction (non-tetanic
contraction); however, the muscles are still able to generate a
functional task. For stimulation frequencies below 16 Hz
continuous, (tetanic) muscle contraction is very unlikely. The
higher the stimulation frequency, the faster the muscles fatigue
and the lesser the discomfort experienced by the patient. Within
pulse frequencies of about 0 to 100 Hz, the stimulation frequency
generally determines the rate of APs. Beyond 100 Hz, the rate of
APs in not necessarily proportional to the amount of stimulation
frequency. Stimulation frequencies above 1,000 Hz may incapacitate
excitable tissues and thus not generate APs.
[0077] Pulse polarity and symmetry: Pulses may be monopolar
(positive or negative) or bipolar (positive and negative). Bipolar
pulses can be symmetric or asymmetric. The different permutations
of these characteristics are illustrated, for example, in FIG.
1.
[0078] The abovementioned characteristics define the type and shape
of pulses used in FES applications. For external stimulation, for
example, the charge balance on the tissue is preferably maintained
as excess charge build up in the tissue over time can result in
galvanic processes and cause significant tissue damage and pain.
For this reason, bipolar pulses that apply the same amount of
charge in each direction are used most often in clinical practice.
An asymmetric pulse with one negative phase at a given amplitude
and duration and one second positive phase at one quarter the
amplitude for 4 times the duration are believed to produce improved
results for external FES applications, however, other pulse
duration and amplitude ratios may also be considered in the present
context without departing from the general context of the present
disclosure. Depending on the application at hand, improved accuracy
and control on pulse stimulation parameters may allow for a more
accurate and effective treatment, not to mention improved patient
safety and comfort levels. For example, the provision of reduced
pulse rise times (which may effectively contribute to a reduction
in pulse amplitudes (energy) utilized to generate desired muscle
contractions), tight control over pulse temporal characteristics
and pulse amplitude, may all contribute to a reduction in the
likelihood of charge build up, and thus represent a constant
opportunity for FES system improvements.
[0079] With reference to FIG. 3, and in accordance with one example
embodiment, an exemplary output stage 300 is generally depicted. In
this example, the output stage 300 generally comprises a first
power stage 302 operatively coupled to a power source 304, such as
a battery or the like, to increase the voltage supply available to
implement various FES pulse sequences/parameters to a load 308 via
a switching circuit 310. A controller 312 is also provided to
control various operational aspects of the output stage 300, such
as voltage and/or current regulation and control to regulate FES
parameter values and/or implement various safety procedures, as
well as control operation of the pulse generating circuit in
accordance with one or more selectable FES treatment
sequences/parameters. A general FES microcontroller 314 may also be
provided in providing overall control features, for example in the
context of an overall FES system incorporating output stage 300. In
one embodiment, the first power stage 302 includes a digitally
controlled switch-mode power supply (SMPS). In order to achieve the
desired pulse response time while changing the direction of the
current, (e.g. from V to 1/4V in a short time frame), in one
example embodiment, the first power stage 302 can include, for
example, four SMPS power supplies in series, so that switching or
relaying in of all of the power supplies can result in a total
voltage V, and switching or relaying in only one of the power
supplies can allow the voltage supply to readily drop to 1/4V.
[0080] The switching circuit 310 will now be described in greater
detail. To produce bipolar asymmetric pulses, for example,
stimulation must generally be switched from a positive/negative
current at a given amplitude, followed by a current of the opposite
polarity at a fraction of this amplitude (e.g. from I to -1/4I in
one example). The switching circuit 310 can be used to change the
voltage and current direction of the load quickly, such as by way
of switches in an H-bridge configuration. Accordingly, the output
stage 300 can quickly change the amplitude of the voltage V to 1/4V
as well as the direction of the current flow to the load.
[0081] FIG. 4 is a high level diagram of another example FES system
400, in accordance with an example embodiment. FIG. 5 is a detailed
schematic diagram of the FES system 400. The FES system 400 may
include a tablet computer 402, a power supply 404, a battery 406, a
processor board 408, one or more stimulation boards 410 (eight
stimulation boards shown), and a plurality of output channels 416
(eight output channels shown).
[0082] In an example embodiment, the battery 406 is selected for
12V to 16.8V, 2000 mAH with a 2 A max charge/discharge current.
This lower power rating was found to provide greater stability and
less prone to disruptions. In an example embodiment, each generated
constant voltage pulse can include a faster rise time resulting in
a lower required specified target steady state current than when
compared to a rectangular constant current pulse (due to the
capacitance of the patient or other elements) or a constant voltage
pulse having a slower rise time requiring a higher required
specified target steady state current. The system can, for example,
can save the amount of power consumed or total energy required to
be provided by the power source (e.g. less current required per
pulse as well as overall lifetime of the battery 406 than compared
to other systems have a higher current draw).
[0083] A computer device such as the tablet computer 402 includes
at least a memory, a device controller, a display screen, a
communications subsystem (e.g. wireless and/or Ethernet) to
communicate over a local area network and/or the Internet, and a
user input device such as a touchscreen. The tablet computer 402
facilitates operator ease of use. Displayed on the tablet computer
402 is a user interface. The tablet computer 402 can connect to the
Internet for transfer of prescriptions and patient data, described
in greater detail herein. The tablet computer 402 is also used to
control the processor board 408 and effectively the stimulation
boards 410. The controls are typically isolated so as not to damage
the tablet computer 402 and to isolate the patient from earth
ground and line voltage. Example controls on the user interface can
provide the user with an option to specify a treatment protocol for
the particular patient, such as the target steady state current
value, the pulse width, the pulse frequency, and any changes of
these parameters over time. Through the user interface, in some
example embodiments, the user can pre-plan these and other
parameters as a procedure by storing the plan in memory (or other
remotely accessible storage devices), for implementation by the
processor board 408.
[0084] The processor board 408 runs a real-time operating system in
order to control the delivery of the stimulation pulses, in
accordance with some example embodiments. The processor board 408
may include an ARM7 microprocessor, for example. This connects to
the eight stimulation boards 410, which are individually operably
connected to eight output channels 416, for example. The processor
board 408 can also be activated using manual switches such as
footswitch 412 and/or handswitch 414. Other inputs such as external
sensors or control feedback sensors (not shown here) may also be
coupled to the processor board 408 or stimulation boards 410. In
some example embodiments, these switches 412, 414 may be dead-man
switches, meaning the user must hold down the switch to start the
treatment, and releasing the switch automatically stops the
treatment.
[0085] The communication protocol provides a method for
transferring new treatment programs from the tablet computer 402 to
the processor board 408. Once the program is loaded, it is stored
in the non-volatile eeprom memory, for example. The treatment
program defines the pulse characteristics (such as frequency,
amplitude, pulse duration, pulse type, and pulse train profile(s)).
The program also specifies the duration of the treatment and how it
is triggered (for example through analog or digital user input).
The commands allow the tablet computer 402 to instruct the
processor board 408 to start a treatment, pause a treatment, resume
treatment, stop a treatment. The status information from the
processor board 408 includes data from the isolated digital/analog
patient inputs (envelope information only) and alarm
information.
[0086] The user interface application of the tablet computer 402
can be configured to handle the following tasks:
[0087] 1. Treatment selection. This involves selection appropriate
treatment for the patient. It also may involve creating/editing
existing treatments or loading new treatments through a service USB
or download treatments from the Internet.
[0088] 2. Sending configuration file to the stimulator. It is
assumed that a new file is sent to the microcontroller board each
time a treatment starts. The treatment file is a script of actions
that the stimulator boards carry out. The tablet computer 402
translates the script into a compressed binary script. The basic
functions of the script file are as follows:
[0089] Start condition: defines input state and perhaps phase of
the treatment to execute the procedure. For example waiting for a
button press.
[0090] Synchronization to other channels. Waiting for other
channels to complete their control loops.
[0091] Running parameters: defines frequency, pulse type and
amplitude, allowed current range for the output (two sets of
thresholds: warning and error levels).
[0092] Loops for repeating sequences.
[0093] Terminating conditions (such as time out, change in input
state).
[0094] 3. Reading and displaying serial number, firmware version of
the microcontroller. The tablet computer 402 reads status
information such as error flags, battery level, currently applied
pulse type, pulse frequency, pulse duration, target output current,
and actual average positive and negative current levels for each of
the outputs.
[0095] 4. Reading and displaying the status of the 4 ADC input
values.
[0096] 5. Start/stop treatment. Pressing a button on the touch
screen starts and stops the treatment. The unit contains a power
button that is used to stop the treatment in the event that the
tablet computer 402 becomes unresponsive. In some example
embodiments, starts and stops on the user interface can be
implemented as dead man switches, meaning the user must hold down
the button to start the treatment, and releasing the button
automatically stops the treatment.
[0097] 6. The tablet computer 402 manages its own power to minimize
the power consumption.
[0098] Referring to FIG. 5, an enclosure 420 can house the
components of the system 400. The enclosure 420 and connector
cables may include plastic or other non-conductive material. The
enclosure 420 can have an internal shield. At least some of the
connector cables including cables 422, 424, 426 can be treated with
ferrites or other suitable materials in order to block or reduce
electromagnetic interference.
[0099] Referring to FIG. 5, status LEDS 418 can include red, green
and yellow status LEDs which are mounted in the enclosure and
connected to the processor board 408. The status LEDs 418 are used,
in some example embodiments, to indicate AC power status (green LED
on or off), treatment running (yellow LED flashing), and error (red
LED on).
[0100] FIG. 6 is a detailed schematic diagram of one output stage
600 of a FES system, such as the FES system 400 (FIG. 4), in
accordance with an example embodiment. The output stage 600
includes a controllable constant voltage pulse generator. For
example, each of the eight output channels 416 (FIG. 4) may be
driven by a respective output stage 600, to apply a signal to an
area of the patient 650. In some example embodiments, all channels
416 can have the same frequency, and the leading edges of the
pulses can be synchronized (e.g. to within 10 us). In other example
embodiments, at least some or all of the channels 416 may have
different frequencies. In some example embodiments, at least some
or all of the channels 416 may have different phases (e.g. phase
shifted or with different leading edges).
[0101] Referring still to FIG. 6, the output stage 600 may include
a substantially constant voltage supply 602 having a controllable
output voltage, a switching circuit 604, a controller 606 (e.g.
microprocessor 606), a relay 608, an alternate path 610, and a
signal detector 612. The substantially constant voltage supply 602
can include four power supplies 614a, 614b, 614c, 614d (each or
individually referred to as 614) in series, which can each be 45 V,
for example. In some example embodiments, these four power supplies
may be used because these parts are easier to supply and less
expensive than one large power supply. Further, this allows the
voltage to be readily divided to provide asymmetric pulses. For
example, one power supply 614a can be tapped for applying a
negative voltage which is one quarter of the positive voltage. In
other example embodiments, more or less power supplies 614 can be
used, such as one or two.
[0102] The power supplies 614 each charge a respective large
capacitor 616a, 616b, 616c, 616d (each or individually referred to
as 616). This allows the capacitor 616 to discharge to provide the
large current spike at the start of the pulse. In another
embodiment, the substantially constant voltage supply 602 can
include a power supply that was able to deliver suitable amounts of
current, which may not need the capacitors 616. However, using
capacitors in this manner allows using of smaller power supplies
614, saving cost, heat generated, and space. Additional large
capacitors 622, 624 can be used to store charge to provide the
required amounts of current. The large capacitors 622, 624
therefore provide charge to allow fast pulse rise times which are
predominantly defined by the switching speed time of the switches
in the switching circuit 604. The particular power supplies 614
that are used can be adjusted to provide 2 to 45 volts each, for a
total of 8 to 180 volts, for example.
[0103] Each power supply 614 may each include an isolated DC-DC
module 630a, 630b, 630c, 630d (each or individually 630). Each of
the outputs from these are regulated by a respective linear
regulator 632a, 632b, 632c, 632d (each or individually 632). The
voltage of each regulator 632 is set by a respective digital
potentiometer 634a, 634b, 634c, 634d, which can be for example a
maximum of 100 k ohms. The output of each regulator 632 is
connected in series creating a variable output supply with a range
of 8V to 192V. The effective range of the supply is adjusted to
2.5V to 160V. The achievement of the specific minimum value 2.5V is
explained in greater detail herein with respect to the Zener diode
618.
[0104] The microcontroller 606 uses a Serial Peripheral Interface
(SPI) port to send data to the digital potentiometer 634 to set the
voltage of each of the 4 linear regulators 632. The data to each
potentiometer 634 can be sent independently to each other. The
first regulator 632a (connected to the common) can use an
additional digital potentiometer, such as 100 k ohm potentiometer
636, to achieve greater resolution. The high regulator 632d
(connected to high voltage output) can use an additional 20 k ohm
potentiometer 638, to achieve greater resolution (at 45V output the
individual regulator has a maximum step size of 0.2V). Regulators
632b and 632c can use only the single 100 k digital potentiometer
634b, 634c, for example.
[0105] The most power intensive pulse type is expected to deliver 4
W. Each of the power supplies 614 can be used to charge the large
capacitor 616 (e.g. 470 uF or larger). The maximum ripple during
normal operation is expected to be <24 VDC (based on two 16 ms,
125 mA pulses). During normal operation, the maximum current from
the DC-DC supply is limited to 60 mA (using a 100 Ohm resistor with
maximum ripple 6 VDC on each module).
[0106] In order to provide a minimum voltage of about 2.4 volts, a
Zener diode 618 is provided at the output of the voltage supply 602
to the switching circuit 604. The output voltage is dropped by 5.6V
as a result of the Zener diode 618. A 1.4V voltage drop applies for
the 1/4 negative supply as a result of Zener diode 620, providing a
minimum of 0.6V. The upper range is limited by regulation error and
supply ripple. The required voltage level settings of the power
supplies 614 can take into account the voltage drop from the Zener
diodes 618, 620 to the patient 650.
[0107] The switching circuit 604 can include an "H bridge"
configuration composed of several metal-oxide-semiconductor
field-effect transistor (MOSFET) switches, for example four
n-channel MOSFET switches 640, 642, 644, 646. This circuit
configuration allows the current to flow though the patient 650 in
either a positive or negative direction, using switching control of
the switches 640, 642, 644, 646. For example, a positive pulse can
be activation of switches 640, 646, while a negative pulse can be
activation of switches 642, 644. The rise time of the voltage pulse
is primarily determined by the switching speed of the MOSFET
switches 640, 642, 644, 646. The relay 608 can be used to select
all of the power supplies 614a, 614b, 614c, 614d to apply a
relatively high specified voltage level. The relay 608 can be used
to activate one of the power supplies 614a to readily apply
one-quarter of the voltage level (e.g. for asymmetric bipolar
pulses).
[0108] The MOSFET switches 640, 642, 644, 646 are operated by
high-side/low-side drivers with bootstrap capacitors. Between
pulses the low-side MOSFET switches 644, 646 can be activated,
shorting patient electrodes together. The MOSFET signals are
operated by the microcontroller 606.
[0109] The H-bridge circuit is used to control patient pulses, such
the start and stop of each pulse using the signals from the voltage
supply 602. For symmetric pulses, positive and negative pulses are
powered by the four power supplies 614 in series. For asymmetric
pulses, the positive pulse is powered by the four power supplies
614 in series. However, the negative pulse of the asymmetric pulse
can be powered by a single power supply 614a, which generates 1/4
of the voltage from the high voltage supply. The voltage selection
between symmetric and asymmetric pulses is done with the latching
relay 608.
[0110] Referring to signal detector 612, this can be used for
current measurement, for example the steady state current that is
being applied to the patient 650. Typically, this current value is
measured near the end of the pulse. The current generated from the
H-bridge circuit 604 is measured using shunt resistor 648. It was
found that increased resistance of the shunt resistor 648, greater
than 10 Ohms, provided more favourable and consistent measurements.
The current reading is connected directly to the pins of the
microcontroller 606 and measured using the internal analog-digital
converter (ADC). The measured value is processed by the
microcontroller 606 to calculate resistance between electrodes. The
processor measures the current (steady state) for the positive
pulse, for the negative pulse (steady state), current through the
test load, and the off current. The readings (envelope) are stored
as status to be sent back to the processor board 408 (FIG. 5).
[0111] Referring to another signal detector 652, this can be used
for voltage monitoring. The microcontroller 606 reads the supply
voltage connected to the positive pulse output voltage across the
patient and the negative pulse output voltage across the patient.
The processor measures the voltage of the positive pulse supply,
negative pulse supply, and digital supply. The readings (envelope)
are stored as status to be sent back to the processor board 408
(FIG. 5). Note that the signal detectors 612, 652 may be readily
used to calculate the present patient capacitance, if desired.
[0112] In some example embodiments, the information detected by the
detectors 612, 652 can be stored in a local memory, and/or sent to
a remote server. In some example embodiments, the system can be
used for monitoring the patient's skin resistance, and the skin
resistance "profile" can be used to determine if a wrong person is
being delivered the therapy instead of the person for whom the
therapy was originally prescribed. This may include the native
impedance parameters, and/or any responses to FES treatment
parameters. The patient profile can be used as a signature for that
patient. This can be used, for example, to prevent fraud and to
monitor what the stimulator has been used for during previous
treatments.
[0113] Referring to the alternate path 610, the output circuit
contains a p-channel MOSFET switch 658 and a 500 ohm test load 660.
The load 660 can be activated independent of the H-bridge 604. The
test load 660 is used to test the current measurement and power
supply circuits before the treatment. The test load 660 is also
used to discharge high voltage supply (the output capacitance of
the power supply is approx 3.3 uF) if output voltage for the next
pulse needs to be lower than the current pulse.
[0114] Generally, as described above, the stimulation pulse is a
constant voltage pulse. However, the stimulation dose is specified
in terms of target steady state current, for example as received or
specified by the practitioner via the tablet computer 402 and
processor board 408 (FIG. 5). The steady state current is the
current through the electrodes at the end of a positive pulse
(after an exponential decay). To achieve this, the microprocessor
606 measures the current actually delivered, calculates the steady
state resistance of the patient 650, and adjusts the voltage to
deliver the desired current. This is done by passing the current
through the shunt resistor 648 in series, and then measuring that
voltage with an analog to digital converter. The microprocessor 606
does the calculation and sends out the control signals to adjust
the voltage. The initial calibration is first performed using a few
sub-threshold pulses (that do not actually stimulate the patient
and cannot be felt). After the real stimulation starts, the
measurement is repeated during every pulse to ensure that the
resistance is not changing. Constant voltage pulses are suitable
for this application since the patient resistance typically does
not materially change within any given pulsewidth.
[0115] Each stimulation channel is capable of generating
asymmetrical/symmetrical biphasic waveforms with following
characteristics:
[0116] Target current range 0 to 125 mA. Adjustment in 0.05 mA
steps for current setting below 5 mA, 0.1 mA steps for current
setting between 5 mA and 15 mA, 0.5 mA steps for current setting
above 15 mA. Steady state target output current error +/-0.5 mA for
currents up to 15 mA. Steady state target output current error +/-1
mA for currents above 15 mA. The maximum current may be limited by
the skin resistance and the maximum output voltage of the circuit.
The minimum current may be limited by the skin resistance and the
minimum output voltage of the circuit.
[0117] The actual amplitude levels may be limited by software
depending on frequency. With a load resistance of 500 ohms, the
steady state output current can be set to not exceed 80 mA at DC,
50 mA between DC and 400 Hz, 80 mA between 400 and 1,500 Hz, and
100 mA above 1,500 Hz.
[0118] When operating the stimulator with actual patient there will
be an inrush current at the start of the pulse. The pulse width
range can be from 0 to 16,000 us (adjustment in 10 us range, output
error 10 us). Pulse width may be limited by the frequency setting.
Minimum time between pulses is 200 us. The pulse frequency can be
from 1 to 2,000 Hz (adjustment in 1 Hz step, output error 1
Hz).
[0119] The maximum average output power can be limited to 4 W for
each channel (the most power intensive asymmetric pulse is 125 mA
(800 us) positive pulse, 31 mA (3.2 ms) negative pulse, frequency
of 100 Hz). The most power intensive symmetric pulse is 125 mA (800
us) positive pulse, 125 mA (800 us) negative pulse, frequency of
100 Hz.
[0120] The maximum voltage generated by the output stage for the
asymmetrical pulses can be 160 VDC for positive pulse and 40 VDC
for negative pulse.
[0121] The maximum voltage generated by the output stage for the
symmetrical pulses can be 160 VDC for positive pulse and 160 VDC
for negative pulse.
[0122] The minimum voltage generated by the output stage for the
asymmetrical pulses can be 2.5 VDC for positive pulse and 0.6 VDC
for negative pulse.
[0123] The minimum voltage generated by the output stage for the
symmetrical pulses can be 2.5 VDC for positive pulse and 2.5 VDC
for negative pulse.
[0124] The rise time of the pulse is under 2 ns (rise time measured
from 10% value to 90% value) measured at the output of the
stimulator with standard skin model load. Slightly longer rise
times (<50 ns) may be used to minimize electromagnetic
emissions.
[0125] The maximum voltage across patient leads can be 500 VDC.
[0126] The target skin resistance is in the range of 500 Ohm to 10
kOhm. At higher skin resistance values, the output current will be
limited by the skin resistance. 125 mA is supported on skin
resistance up to 1,280 Ohm. 50 mA is supported on skin resistance
up to 3,200 Ohm. At 10 kOhm the maximum current that can be
supplied is 16 mA. Minimum current for 500 Ohm is 5 mA (2.5V
minimum output). Adjustment step size increases with the output
voltage. At the highest voltage the step size is 0.2V which
produces the maximum 0.4 mA current step size at 500 Ohm load.
[0127] Low voltage short series "calibration pulses" (with
amplitude below 10V) are applied before the start of the treatment
to measure the resistance of the electrode/skin. If the pulse
duration, as dictated by the protocol, is less than 100
microseconds, then the voltage for these pulses is delivered based
on "calibration pulses" only. If the pulse duration is greater than
100 microseconds, the skin resistance is re-measured after each
pulse and the voltage is adjusted.
[0128] Sample current, skin resistance and step size are as
follows:
[0129] For 0-5 mA, 500 Ohm: output voltage range: 0-2.5V with 0.05
mA step size this requires 0.025V step size (the minimum output of
the circuit is 2.5V). For 0-5 mA, 2,000 Ohm: output voltage range:
0-10V with 0.05 mA step size this requires 0.1V step size (the
minimum output of the circuit is 2.5V). For 0-5 mA, 10,000 Ohm:
output voltage range: 0-50V with 0.05 mA step size this requires
0.5V step size (the minimum output of the circuit is 2.5V).
[0130] For 5-15 mA, 500 Ohm: output voltage range: 2.5-7.5V with
0.1 mA step size this requires 0.05V step size. For 5-15 mA, 2,000
Ohm: output voltage range: 10-30V with 0.1 mA step size this
requires 0.2V step size. For 5-15 mA, 10,000 Ohm: output voltage
range: 50-150V with 0.1 mA step size this requires 1V step
size.
[0131] For 15-125 mA, 500 Ohm: output voltage range: 7.5-62.5V with
0.5 mA step size this requires 0.25V step size. For 15-125 mA,
2,000 Ohm: output voltage range: 30-150V with 0.5 mA step size this
requires 1V step size. For 15-125 mA, 10,000 Ohm: output voltage
range: 150-160V with 0.5 mA step size this requires 5V step size
(maximum current is limited due to voltage limitation).
[0132] In some example embodiments, the system 600 of FIG. 6 can
therefore be used to apply the signal pulses to the patient which
are illustrated in any one of FIGS. 9 to 12.
[0133] FIG. 13 is a flow diagram of a method 1300 for applying
signal pulses to a patient, in accordance with one example
embodiment. The method can be implemented by a controller or
microcontroller, for example. The flow diagram 1300 can also
represent functional modules or blocks, which can be state-based.
The method 1300 is for controlling a functional electrical
stimulation system for providing pulse stimulation to an area of a
living body by way of one or more electrode leads applied to the
area, the area including an associated resistance element and an
associated capacitance element, wherein the electrical stimulation
system includes a pulse generating circuit having a controllable
output voltage to generate constant voltage pulses to the one or
more electrodes, wherein the corresponding current signal of each
constant voltage pulse includes a spike followed by an exponential
decay to a steady state current value.
[0134] At event 1302, the method 1300 includes determining
specified target parameters, including at least a specified target
steady state current value to be applied to the area. At event
1304, the method includes determining the present resistance of the
patient. At event 1306, the method includes controlling the pulse
generating circuit to generate a constant voltage pulse to the one
or more electrode leads at a calculated voltage level which
achieves the specified steady state current value to the area.
[0135] Referring to event 1302, the specified target steady state
current value can be input by a practitioner or user, for example
through a user interface of a tablet computer, or by accessing the
specified target steady state current value from a pre-programmed
dosage schedule stored in a memory or remote server.
[0136] Referring to event 1304, a signal detector can be used for
detecting signal parameters associated with the area of the living
body, such the actual steady state current that is being applied.
The applied voltage to the patient is also known or can be detected
using a voltage detector. This can be used to calculate the present
resistance of the patient. In some example embodiments, the present
resistance can be estimated for each pulse, or periodically (e.g.
one pulse in every specified number of pulses or time duration), or
can be calculated as an average resistance (or moving average) over
a specified number of pulses or a period of time. The resistance of
the patient can be initially estimated by applying one or more
sub-threshold pulses (e.g. non AP stimulating) to the area from the
pulse generating circuit, prior to the start of the actual
procedure.
[0137] Referring to event 1306, the calculated voltage level is
calculated from the associated resistance element of the patient
and the specified target steady state current value using Ohms' Law
(e.g. V=R*I). Note that, in some example embodiments, the
calculated voltage level is calculated without consideration of a
value of the associated capacitance element.
[0138] The method 1300 can be configured in a loop, as shown. For
example, in the next iteration, referring again to event 1302, the
method 1300 may include determining the next specified target
steady state current value to be applied to the area (this step can
be skipped if the value is the same). At event 1304, the method
1300 includes determining the present patient resistance (e.g.
based on the presently detected patient readings of the previous
pulse). At event 1306, the method 1300 includes controlling the
pulse generating circuit to generate the next constant voltage
pulse to the one or more electrode leads at the next calculated
voltage level which achieves the next specified steady state
current value to the area.
[0139] The constant voltage pulses may provide sequential bipolar
pulse stimulation, which includes a pulse sequence including a
positive constant voltage pulse and a negative constant voltage
pulse.
[0140] FIG. 14 is a flow diagram of a method 1400 for applying
signal pulses to a patient, in accordance with one example
embodiment. The method can be implemented by a controller or
microcontroller, for example. The flow diagram 1400 can also
represent functional modules or blocks, which can be state-based.
The method 1400 is for controlling a functional electrical
stimulation system for providing pulse stimulation to an area of a
living body by way of one or more electrode leads applied to the
area, the area including an associated resistance element and an
associated capacitance element, wherein the electrical stimulation
system includes a pulse generating circuit having a controllable
output voltage to generate constant voltage pulses to the one or
more electrodes, wherein the corresponding current signal of each
constant voltage pulse includes a spike followed by an exponential
decay to a steady state current value.
[0141] At event 1402, low voltage short series "calibration pulses"
(with amplitude below 10V) are applied before the start of the
treatment to measure the initial resistance of the electrode/skin.
These can be, for example, non AP stimulating pulses.
[0142] At event 1404, the method 1400 determines specified target
parameters for a given dosage. The target parameters may include
steady state current value, pulse width, pulse frequency and
duration at that steady state current value. As well, the pulse
type can be specified as symmetric or asymmetric for bipolar
pulses. These parameters can be retrieved from a treatment file
stored in memory, or adjusted in real-time by the practitioner, for
example.
[0143] At event 1406, in some example embodiments, a bipolar pulse
sequence is generated. It can be presumed that the "bipolar pulse
sequence" can be a pulse pair comprising one positive pulse
followed by one negative pulse. For most frequencies, further
processing (e.g. events 1408, 1410) may be performed between
adjacent pulse pairs. Event 1406 includes controlling the pulse
generating circuit to generate a constant voltage pulse having the
target parameters of steady state current value, pulse width, and
pulse frequency. The constant voltage pulse has a calculated
voltage level which achieves the specified steady state current
value to the area.
[0144] Referring to event 1408, the method includes determining the
present resistance of the patient. A signal detector can be used
for detecting signal parameters associated with the area of the
living body, such the actual steady state current that is being
applied. The applied voltage to the patient is also known or can be
detected using a voltage detector. This can be used to calculate
the present resistance of the patient. In some example embodiments,
the present resistance can be estimated for each pulse, or
periodically (e.g. one pulse in every specified number of pulses or
time duration), or can be calculated as an average resistance (or
moving average) over a specified number of pulses or a period of
time.
[0145] At event 1410, after completion of one bipolar pulse
sequence (e.g. one positive pulse followed by one negative pulse),
it is determined whether the specified duration (at the target
steady state current) has been completed. If not, the method 1410
returns to event 1406, wherein the next voltage level is calculated
for the next bipolar pulse sequence, which accounts for any changes
in patient resistance determined at event 1408. This allows the
same specified target charge to be consistently applied to the
patient. If the duration has completed (if "yes"), at event 1412,
the next target parameters are determined for the next dosage level
(target steady state current), which is again determined at event
1404.
[0146] It will be appreciated that alternative measures may be
implemented in adapting control sequences and circuitry to the
different embodiments, and that, without departing from the general
scope and nature of the present disclosure.
[0147] Some example embodiments herein described may, for example,
promote sustainable implementation and wider adoption of emerging
FES applications that are presently only available as research
tools given the deficiencies and drawbacks of known devices, as
described above. Also, some embodiments may provide simultaneous
pulses over multiple channels.
[0148] Another parameter of interest in these applications is the
rise time, i.e. the slew rate of the electrical pulses, which, in
general, should be as fast as possible. Namely, the relevance of
providing a fast rise time in these pulses stems from the
physiology of excitable tissues, namely nerve and muscle cells, and
the generation of action potentials. These tissues have ion pumps
that work against the delivered charge of an electrical pulse to
maintain the nominal potential difference on the cell membrane.
Pulses with a higher slew rate may give less time to the ion pumps
to compensate for the delivered charge, allowing stimulation with
lower amplitude signal. The advantages of stimulating with lower
amplitude pulses may include more comfortable (i.e. less painful)
therapy and a longer battery life of the device, for example.
[0149] Another consideration is that voltage activated sodium and
potassium gates, that essentially generate action potentials, are
triggered by a local change in the nerve membrane potential. These
voltage activated sodium and potassium gates behave in a
statistical fashion, i.e., each voltage gate has its own voltage
level that triggers it which slightly deviates for the average
trigger level. Therefore, fast delivery of charge (i.e., fast pulse
slew rate) to all voltage activated sodium and potassium gates will
ensure that all gates are triggered, ensuring higher success rate
of generating action potentials. In the event that the charge is
delivered more gradually, it is possible that a number of voltage
activate gates will not be triggered. Therefore, in order to
achieve more reliable response with pulses that have slower slew
rate, one may need to deliver more charge, i.e., one would need to
use the stimulation pulses with higher amplitude to activate
critical number of voltage triggered gates. Therefore, the fast
pulse slew rate has a potential to generate more reliable action
potential production in the excitable tissue using less charge.
[0150] Furthermore, the device described herein in exemplary
embodiments may provide improved pulse rise times and more accurate
amplitude and duration control. These faster rise times may allow
the potential to achieve the same tissue stimulation results with
less steady-state current. This may in turn reduce the stress on
the individual (i.e., perception of pain or discomfort) as well as
decreases the energy consumption of the stimulator. The rise time,
in combination with the accurate amplitude and duration control
also may provide that over time no charge will be built up in
stimulated tissues, which can be an important aspect for FES
applications, especially for applications involving implanted FES
systems.
[0151] In some embodiments, the slew rate of the pulses produced by
the herein described systems and designs are significantly faster
than the 1 .mu.s slew rates common to some existing devices and
systems. For example, in one embodiment, a pulse slew rate of no
more than 500 ns is achieved. In accordance with another
embodiment, a pulse slew rate of no more than 100 ns is achieved.
In accordance with yet another embodiment, a pulse slew rate of no
more than 8 ns is achieved. In accordance with yet another
embodiment, a pulse slew rate of no more than 5 ns is achieved. In
accordance with yet another embodiment, a pulse slew rate of no
more than 2 ns is achieved. In accordance with yet another
embodiment, a pulse slew rate of no more than 10 ns is achieved.
Accordingly, the pulse slew rates may, in some embodiments, be as
much as two orders of magnitude faster than conventional
systems.
[0152] In one embodiment, the provision of such improved pulse rise
times may also or alternatively allow for a reduction or
minimization of physical discomfort experienced by a patient as a
result of the pulse stimulation. For example, by applying a reduced
charge to the stimulated tissue, or again by achieving greater
tissue responsiveness, treatments implemented using the herein
described device may reduce, if not completely avoid patient
discomfort.
[0153] As will be appreciated by the skilled artisan, the highly
flexible architecture of the above-described embodiments and
below-provided examples may be particularly suitable for the
implantation of battery-powered external functional electrical
stimulators (FES) and neuroprostheses, and readily amenable to
emerging sophisticated FES applications, such as closed-loop
controlled and brain machine interfaced neuroprostheses, for
example, as well as various other applications.
[0154] Reference is now made to FIG. 23, which shows is an example
high level diagram of a communication system for one or more FES
systems, in accordance with an example embodiment. The system
design incorporates multiple subsystems that together create the
required components for the administration and delivery of FES
therapy to patients. As shown in FIG. 23, there can be three main
subsystems as part of the overall system; Stimulator, Local
Interface, and Backend Data Management System (BDMS).
[0155] The Stimulator System is a system which is used to provide
stimulation treatment (protocol) to a patient. The main components
of the system are an ARM7 Microprocessor, the software running on
the ARM7 (stimulator application), as well as custom electronics
and physical electrodes which interface between the ARM7 and the
human body. The stimulator application calculates the appropriate
stimulation level based upon the protocol type and transmits this
analog output to the human body via the connected electrodes.
[0156] The Stimulator application is command based and event
driven. Its main function is to listen for commands, decode these
commands, and execute them accordingly. As a result, the Stimulator
device can be controlled by another application if it can establish
a valid communication path and send the correct commands as defined
by the Application Programming Interface (API) for the device.
[0157] The local interface is the primary interface used by the
therapist to configure, setup and administer the actual treatment,
including user interface to view data and control the system. This
subsystem will interface to the stimulator to administer the actual
treatment protocols as well as the Backend Data Management System
to manage patients, prescriptions, therapists as well as
synchronize treatment details between multiple devices in a
practice.
[0158] The Backend Data Management System is used to manage the
overall treatment process including Device ID's, Therapist ID's,
Patient IDs (PUID's), prescriptions and primary report interface.
This cloud-based system can also allow for synchronization between
multiple devices in the field. Access to patient data can be made
over secure Internet connections and other communication mediums
through the Backend Data Management System.
[0159] In accordance with some example embodiments, the FES system
can be used to assist with the "bioinfomatics" use of the device
and the patient receiving treatment. For example, the system can be
used for capturing, in memory, information of the pulses applied
during treatment, sending to a central repository (e.g. Backend
Data Management System), and providing this information from the
central repository to one or more of patients, clinicians, clinics,
administrators, third party payors, and other information relating
to the patient, treatment or use of the system. The information can
be used to determine, automatically or manually, best protocols or
treatment options based on prior results such as successes and
failures.
[0160] Many government and private insurance programs are under
increasing pressure to limit healthcare expenditures and are
adopting various measures to control costs. These measures include,
but are not limited to healthcare reform measures,
pay-for-performance, Comparative Effectiveness Research, and group
purchasing. Increasingly, third party payers are converging on a
set of common criteria in the assessment of whether a technology
improves health outcomes such as length of life, quality of life
and functional ability.
[0161] Insurers generally seek evidence that a new therapy
represents an efficient use of healthcare resources. Ongoing
clinical studies and the aggregated database of patients that have
been prescribed patient "keys" will capture and provide the data to
support reimbursement.
[0162] This assists with payment by health care systems. There is
increasing pressure on hospitals to discharge patients more rapidly
and preferably to discharge them to their homes. Patient discharge
from in-patient rehabilitation hospitals is determined by a number
of factors, including the attainment of certain functional
independence goals.
[0163] In another aspect, the system can be used to provide a
method for prescribing a treatment to a patient. For example, the
system can be used for receiving a "prescription" purchase request,
and providing a patient dedicated electronic key in response to the
purchase request. The electronic key can include: access to
protocol(s) for a prescribed therapy intervention; a record of the
pattern of use of the protocols, including at least duration,
frequency and amplitude of pulses to be applied to the patient;
outcomes captured during treatment; and reports on progress and
treatment planning.
[0164] FIG. 24 is an example flow diagram of user interface screens
on a computer device for controlling and managing an FES system, in
accordance with an example embodiment. The graphical user interface
on the clinical based workstations and portable stimulator devices
will be direct users to protocols, diagnostics that report patient
progress, and/or instructional material including videos, help
menus and user manual.
[0165] Referring to FIG. 24, the home screen is presented to the
user upon successful start of the application. The home screen
presents the following navigation choices: Patient Treatment,
Settings, and Help. The home screen also displays the current
stimulator device battery level, therapist login, and patient login
may be implemented using identifiers and passwords. Referring to
the Therapist Login screen, after selecting Patient Treatment on
the Home Screen the Therapist Login screen will be displayed
prompting for the keyed entry of a Therapist ID and password. Once
the OK Button is pressed the UI task will take the entered values
of the Therapist ID and Password and query the database for
validity. If the Cancel Button is pressed the UI will return to the
Home Screen. Once the Therapist logs in, the User Interface will
prompt the user for a Patient ID (PUID). The device again queries
the database for validity once the OK button is pressed. If the
Cancel button is pressed the UI returns to the Home Screen.
[0166] Once logged in, various example screenshots of the user
interface screens in FIG. 24 are illustrated in FIGS. 25 to 31.
After successful Therapist and Patient login, the UI displays the
Patient Treatment Screen, for example as illustrated in FIG. 25. In
the Patient Treatment Screen the following information is
displayed: Patient Identification; Session History; Available
Protocols; Selected Protocols; and Stimulator Battery Level.
[0167] The Patient Identification data is displayed on the screen,
for example at least patient name (sometimes first name only) and
birth date. The Session History for the patient is a list of
previous session dates associated with the selected Patient ID. The
Session History is from the database and includes the times of
previous sessions. Each date can be selected by the use through the
user interface, for example, resulting in FIG. 26.
[0168] The Available Protocols is a display of Protocols which are
available to the Patient, and is presented to the user through the
user interface. The example protocols shown include 10 second on/10
second off muscle strengthening, Hand-Mouth, Opposite Shoulder,
Side Reach, Side Reach NEW, Forward Reach, Opposite Shoulder and
Lat Reach, Opposite Knee Reach, Lateral Pinch, Pinch Grasp, Tripod
Grasp, and Pinch Grasp variation.
[0169] The Selected Protocols is a display of Protocols
(stimulation parameters) which have been selected for the current
treatment session. These are typically selected by dragging and
dropping from the Available Protocols. The example selected
protocol shown in FIG. 25 is a Hand-Mouth protocol sequence.
[0170] FIG. 26 is an example user interface screen for Session
Details. The Session Details Screen displays information from a
past session (e.g. selecting a particular session date from FIG.
25). It displays the following information: Protocols Used During
Session; Number of Cycles; Total Treatment Time; Individual
Protocol Time; Session Notes; Stimulator Battery Level; and Pulse
Amplitude Per Channel. At least some or all of the information in
the Session Protocol Details can be automatically populated, based
on the system performing the particular protocol(s), in some
example embodiments. The user or practitioner can also edit some of
the fields, including the Adverse Events and the Session Notes to
annotate such information, for example. More or less information
may be displayed, in other example embodiments.
[0171] FIG. 27 is an example user interface screen for Protocol
Details, in accordance with an example embodiment. The Protocol
Details provides a text-based description of the protocol, a
selectable list of the Channels and a viewing window for relevant
image or video files. Images and/or videos are displayed in the
viewing window when a Channel button is clicked. As shown in FIG.
27, the images can include anatomical images for electrode
placement for each protocol. The example shown in FIG. 27 is an
image of the Lumbricals, and the applicable electrode placement.
This provides visual confirmation and verification to the
practitioner of the particular protocol being implemented, for
example. Selection of any specific channel results in the user
interface of FIG. 29 being displayed.
[0172] FIG. 28 is an example user interface screen for Protocol
Setup, in accordance with an example embodiment. The Protocol Setup
allows the user/practitioner to modify the default setup of the max
values per channel. The user does this by selecting the channel to
adjust and then moving the sliders up and down with the respective
controls. The user has the ability to select 1 Hz or 40 Hz
stimulation train while he/she is adjusting the stimulation
amplitude (per channel). 1 Hz stimulation train is typically used
to determine if there is a muscle response at all, and 40 Hz
stimulation trains are typically used to determine the stimulation
intensity needed for the muscle (i.e., stimulation channel) of
interest. The user can also start the selected protocol.
[0173] FIG. 29 is an example user interface screen for channel
setup, in accordance with an example embodiment. For example, this
screen may be accessed by selecting a channel from FIG. 27. The
Channel Setup allows the user to slide the bar within the max or
min values per the selected channel via touching an sliding the bar
or using Up and Down Buttons. The user will additionally be able to
save in memory (and/or to the database) the following values:
[0174] Sensory--the first level that is registered by the
patient;
[0175] Motor--the level where contraction starts;
[0176] Max--the level where max contraction occurs, or where it is
too painful for the level to increase; and
[0177] Treatment amplitude--the level used for treatment.
[0178] FIG. 30 is an example user interface screen for Administer
Protocol, in accordance with an example embodiment. The Administer
Protocol displays the number of cycles and the total elapsed
treatment time along with the amplitude, pulse duration and
frequency for each channel. If a Protocol is paused or stopped, the
user has the ability to resume the protocol from this screen. The
control menu can include user selectable options for Help,
Pause/Start, Stop, Setup and Home.
[0179] The "Setup" button brings the user to the Setup Protocol
User Interface (FIG. 28). The "Pause/Start" button pauses/stops the
treatment and allows for the user to modify the Protocol settings
until the user returns to the administer protocol page.
[0180] FIG. 31 is an example user interface screen for Session End,
in accordance with an example embodiment. The Session Protocol
Details are typically automatically updated based on the protocol
that was just performed. The Session End screen gives the user the
ability to record any adverse events, reasons why treatment was
stopped, and notes when a Protocol(s) is stopped. The adverse
events and reason why treatment stopped may include dropdown menus
and/or checkboxes of predefined reasons. The user records may also
be timestamped, for example to accord with governing policies and
regulatory practices. If multiple protocols were used then details
for each protocol may be recorded by the user.
[0181] One example provides results an exemplary FES therapy
process for improving brain and associated muscle function in
individuals suffering from a neuromuscular deficit, which process
provides an example only of the various FES applications, methods
and treatments that may be facilitated by the above-described FES
devices and systems. In this example, the individual was suffering
from the neurological disorder following a stroke. It will be
appreciated that this kind of neurological disorder of the central
nervous system may have resulted from stroke, spinal cord injury,
brain injury, multiple sclerosis, and any other injury both
traumatic and non-traumatic to the central nervous system, for
example.
[0182] Individual Description: The individual was a 22-year-old
woman who suffered a hemorrhagic stroke in the right frontal
parietal area two years prior to the participation in this study.
The individual presented at an individual rehabilitation centre
with motor recovery status scored by CMSMR (Chedoke McMaster Stages
of Motor Recovery) as follows: arm=1, hand=2, leg=2, and foot=2.
After four months of rehabilitation, the CMSMR scores were as
follows: arm=2, hand=2, leg=4, and foot=2. While left leg showed
some recovery, the left arm was not functional. At the beginning of
the FES-mediated protocol, the individual was independent in
activities of daily living with the help of cane and ankle-foot
orthosis, but reported that she rarely, if ever, used her paretic
upper limb. Movement of the upper extremity was characterized by a
flexor synergy pattern. The individual had increased resistance to
passive stretching in the distal flexor musculature. Tactile
sensation was shown not to be severely impaired throughout the
upper limb by the use of the two point discrimination test. Stroke
patients, such as the individual of the instant study, are
considered neurologically stable and do not show any signs of
further improvement 24 months following stroke. Therefore, the
individual recruited to this study was in the chronic phase of
injury, 24 months post stroke, was severely disable as measured by
CMSMR and was not expected to improve regardless which therapy is
provided to her.
[0183] Functional electrical stimulation therapy: An FES-mediated
protocol was delivered by way of an electric stimulator (electrical
stimulator used was a prototype of the electrical stimulator
discussed above), with standard self-adhesive surface stimulation
electrodes. In the study the following muscles were stimulated with
the surface stimulation electrodes (the locations of the electrodes
for each muscle are shown in the FIG. 15): anterior (aDel) and
posterior deltoid (pDel), biceps brachialis (BB) and triceps
brachialis (TB), extensor carpi radialis, extensor carpi ulnaris,
flexor carpi radialis, and flexor carpi ulnaris. Stimulus
parameters used to stimulate the nerves that are innervating the
muscles of interest were asymmetric bipolar current pulses with the
pulse duration of 250 .mu.sec and frequency 40 Hz. During the
protocol the stimulus was delivered to the muscles of the paralyzed
limb in such a way that these muscles produced movements that
accurately mimicked the movements that the brain would produced if
the patient were not paralyzed. When the stimulus was delivered to
the muscles, it was gradually increased or decreased (instead of
being delivered instantaneously) using ramp up and ramp down
functions lasting from 0.5 to 2 seconds. The therapist used a hand
switch to trigger stimulation when he determined that the
individual needed assistance with the task.
[0184] FES-Mediated Protocol: Briefly, the FES-mediated protocol
consisted of pre-programmed coordinate muscular stimulation and
manual assisted (externally generated) passive motion to establish
physiologically correct movement. During the movement, the
individual was asked to imagine the movements and to try to carry
it out herself. At the beginning of the study the patient was
unable to move the arm voluntarily and therefore was not able to
physically execute voluntarily imagined movements. The FES was
delivered to shoulder, elbow, wrist and finger extensor and flexor
muscles, while the individual (assisted by the therapist) performed
the following types of motions: (1) touch nose, (2) touch shoulder,
(3) move arm forward, (4) lift arm left side up, (5) reach and
grasp large objects, (6) reach and grasp small objects, (7)
manipulate objects during grasp, and (8) place the object at a
designated location and release the object. The FES-mediated
protocol was carried out for an hour. The protocol, at a minimum,
comprises 40 one-hour sessions wherein at least 3 one-hour sessions
are delivered per week, however the protocol may be repeated more
frequently, if desired. In case of the individual of the instant
example, the protocol was preformed twice daily. In individuals who
have suffered a stroke, the neuromuscular recovery typically starts
proximally followed by the recovery of the distal neuromuscular
compartments. Therefore, the FES-mediated protocol began by
training shoulder and upper arm muscles first, followed by wrist
and fingers training.
TABLE-US-00001 TABLE 1 Upper limb motion tasks, types of motion,
and electrodes used for in each task. The alphabetical characters
and numbers in this figure match to those in the FIG. 16. SHOULDER
& ELBOW MOTION Elbow (Elec- Task Shoulder motion (Electrode)
motion trode) Touch nose Flexion a-b Flexion b-c Touch
Flexion&Int. rotation a-b Flexion b-c shoulder Swing Extension
d-e Extension e-f forward Left side up Abduction a-b & d-e
Extension e-f WRIST & HAND MOTION Task Target motion
(Electrode) Bottle grasping Wrist extension & full finger open
1-4, 2-4 & 3-4 Finger flexion 5-6 Small object picking Two
finger (thumb & index) open 1-4
[0185] During the FES-mediated protocol, a therapist
controlled/triggered the arm movements using a pushbutton. During
the movements, the physiotherapist guided the arm and assisted the
individual with the neuroprosthesis in performing the desired task.
This assistance provided that all movements were carried out in a
correct physiological way, i.e., neuroprosthesis induced movements
did not oppose natural joint movements and respected the anatomy of
bone and soft tissue composition. In the early stages of the
treatment, the arm tasks were performed by the combination of
muscular stimulation and therapist's assistance. As the individual
improved, the assistance was reduced to the necessary minimum.
Typically, the stimulation protocols were adjusted weekly or
biweekly. The individual was asked to repeat the same arm task 10
times for each motion during a single treatment session. The
treatment sessions lasted up to 60 minutes.
[0186] Outcome Measures--Clinical assessments: CMSMR and Motricity
Index tests for the upper limb were used to assess the arm and hand
functions. The degree of spasticity in the affected upper limb was
evaluated using the five-grade Modified Ashworth Scale (MAS).
[0187] H-reflex and M max: To assess the excitability of the spinal
motoneuron pool in the flexor carpi radialis (FCR) muscle, the
Hoffman reflex (H-reflex) was elicited. The H-reflex was evoked by
stimulation of the left median nerve with a monopolar electrode
placed in the inside of cubital joint. A rectangular pulse (1 ms)
was generated by a constant voltage stimulator (DPS-007, Dia
Medical System Co., Japan) that was triggered once every 5 s.
[0188] Maximal voluntary contraction (MVC): The electromyographic
(EMG) signals in the following paralyzed upper arm muscles were
detected by a bipolar differential amplifier (Bortec AMT-8; Bortec
Biomedical, Canada): aDel, pDel, BB, TB, flexor capiradialis (FCR),
extensor digitrum longus (EDL), and first distal interosseous
muscles (FDI). A pair of surface electrodes (BiPole; Bortec
Biomedical, Canada) was placed along the muscle fibers over the
belly in each muscle with an inter-electrode distance (center to
center) of 10 mm. The recorded EMG signals were amplified 500 times
and digitized at a sampling rate of 1,000 Hz over a period of 500
ms before and 500 ms after the onset of the movement.
[0189] Active range of motion test: The individual was asked to
move her arm toward following five directions as much as she could:
(1) forward, (2) backward, (3) upward, (4) right side, and (5) left
side. During the movements, we recorded the position of the
shoulder, elbow, and wrist joints, and the second joint of index
finger. The individual did three trials for each of the five
movements.
[0190] Circle drawing test: This test was aimed to assess the
ability to coordinate shoulder and elbow joints. During circle
drawing, the subject requires the ability to coordinate shoulder
and elbow movements. Specifically for individuals whom have
suffered a stroke who have spasm in their elbow joint it is not
easy to draw a wide and a properly shaped circle. The position of
the shoulder, elbow, and wrist joints, and the second joint of
index finger while the individual drew the circle on a table was
recorded. During the assessment the movements were self-paced, and
the task continued for 30 seconds.
[0191] Originally, it was planned to assess the individual using
tests "Outcome Measures--Clinical assessments", "H-reflex and M
max", and "MVC". However, during the first 6 weeks of training the
individual surprisingly showed remarkable improvement of her
shoulder and elbow function, thereby prompting the addition of
tests "Active range of motion test" and "Circle Drawing Test" to
further evaluate functional motion of the upper limb.
[0192] Results: The individual successfully completed all training
sessions and assessments. Following 12 weeks of FES-mediated
protocol, the individual was able to pick a thin object, touch her
nose and draw circles, for example, tasks which could not be
accomplished prior to the FES-mediated protocol sessions. As the
clinical measures selected, namely the CMSMR and Motricity Index
tests are coarse measures, these tests did not show changes in the
scores following the 12-week protocol. However, the MAS of the hand
and wrist showed reduction in spasticity over the course of the
training (wrist: 3 to 2, hand: 4 to 3). H-reflex, which reflects
the spinal motoneuron excitability, also showed remarkable
reduction with training (FIGS. 17 to 19). Namely, the size of the
H-reflex was quite high at the beginning of the protocol (82.09%
Mmax) and as the time passed it decreased considerably (53.65% in
6.sup.th week and 45.04% in 12.sup.th week), indicating that the
high tone which is commonly associated with the damaged to the
supra spinal compartments of the central nervous system is
reverting, and that the central nervous system function is
returning back to its normal levels of tone and reflex responses.
FIG. 20 shows the changes in the MVC in the upper arm muscles
obtained every two weeks. The MVC levels in all muscles measured
were at "zero" during the baseline assessment. In other words, the
patient was unable to activate a single muscle in the affected arm
voluntarily. As the protocol progressed the patient gained ability
to voluntarily activate the muscles and further improved with
continuation of the protocol. It is worth mentioning that the MVC
levels in the affected arm were remarkably smaller than that of the
unaffected arm. However, even the low levels of MVCs were
sufficient to allow the patient to effectively and voluntarily move
the arm and fingers to reach and grasp objects. A good example of
the muscles which showed considerable improvement following the
FES-mediated protocol are the FDI and TB muscles, which did not
show any EMG (RMS .mu.V) activity at the baseline and following the
FES-mediated protocol showed remarkable improvements in voluntary
EMG and muscle contraction control. Table 2 shows the shoulder and
elbow dynamic range of motion. It is clearly shown that the value
of dynamic range of motion for the shoulder and elbow joint at week
12 showed remarkable improvement as compared to those measured at
week 6. At week 0 the individual did not have any voluntary
movement in the affected arm. Therefore, transformation from no
movement in week 0, to restricted movement in week 6 followed by
much more expanded range of motion in week 12 is a remarkable
change. Given that the individual of this study was in the chronic
injury phase, as noted above, and therefore not expected to show
improvement regardless whether any intervention was provided, the
changes observed and noted herein are remarkable. Furthermore, such
changes have not been previously observed in chronic severe stroke
patients.
TABLE-US-00002 TABLE 2 Dynamic range of motion (rom) of the
shoulder and elbow joints. Shoulder Elbow Flexion Abduction Int.
rotation Ext. rotation Extention Direction 6th wk 12th wk 6th wk
12th wk 6th wk 12th wk 6th wk 12th wk 6th wk 12th wk of Motion
(deg) (deg) (deg) (deg) (deg) (deg) (deg) (deg) (deg) (deg) Forward
19.82 28.77 31.25 31.77 74.90 75.36 Upward 34.81 44.25 55.22 62.63
100.78 112.67 Left side 32.51 40.47 22.74 31.84 Right side 52.19
47.35 83.47 108.70
[0193] FIG. 21 shows the x-y plot of the shoulder, elbow, wrist,
and index finger positions while the individual was performing
circle drawing test. The absolute coordinates of individual joints
were represented in the upper three figures in FIG. 21. The joints
and index finger coordinates with respect to the shoulder joint
coordinate frame (i.e., assuming that the reference coordinate
frame is in the shoulder joint) are shown in the bottom three
figures in FIG. 22. While the size of drawn circle by the index
finger was small at the 6th week of the FES-mediated protocol, its
size became larger as the protocol progressed. At week 0 the
individual do not have any voluntary movement in the affected arm
and was unable to drawn circles.
[0194] The purpose of this study was to assess the effect of 12
weeks intensive FES-mediated protocol on a chronic severe stroke
individual (CMSMR score 2 or less). Although motor capacity score,
i.e., CMSMR and MVC tests did not show any significant changes, due
to the courses of the tests, the MAS and the amplitude of H-reflex
were reduced as the result of the FES-mediated protocol.
Additionally, the kinematic results showed a profound improvement
in the ability to perform arm movements and to coordinate shoulder
and elbow joints. These results suggest that the improvement of the
upper arm functional motion can be attributed to retraining of the
central nervous systems through means of neuroplasticity, which is
observed in improvement of the upper limb voluntary motor function
as well as the reduction of muscle tone and/or spasticity.
[0195] Traditionally neuromuscular electrical stimulation has been
used to increase strength of the voluntary muscle contractions in
various neurological patients and healthy individuals. But recent
applications of electrical stimulation are shifting the focus from
muscle strengthening towards re-training the central nervous system
and improving motor control of the stroke individuals. In this
study, FES-mediated protocol was used to retrain a chronic stroke
individual to voluntarily perform coordinated multi-joint movements
with the arm that was previously paralyzed as a result of stroke.
Since the stimulus intensity we used was approximately two times
larger than the motor threshold, one could not expect that the
FES-mediated protocol generated changes in muscular function due to
an associated increase in muscle strength. This assumption was
confirmed by the results shown in the FIG. 20, that is, there were
no consistent changes of the MVC in the upper limb muscles.
[0196] At the beginning of the FES-mediated protocol, the
individual's upper limb had high muscle tone. However, the muscle
tone of wrist and elbow flexors was remarkably decreased as the
result of the FES-mediated protocol, which was clearly reflected by
the results of MAS (Table 1) and H-reflex (FIG. 20). This result
was in good agreement with the previous findings that describe the
effects of the electrical stimulation on the reduction of the
abnormally high muscle tone. It should be noted that the resting
condition of the individual's arm, specifically hand, was
drastically changed with the time course of training. Namely, the
individual was able to relax her hand and keep the hand relaxed
during reaching motion. Therefore, the improvement of the upper arm
functional motion can be partly attributed to the reduction of
muscle tone and/or spasticity. This finding supports the classical
concept that muscle tone reduction represents simplistic solutions
to the deficit in motor control after stroke.
[0197] Pre-programmed stimulus patterns were developed that are
able to generate variety of upper limb movements/functions. The
temporal activations of the muscles induced by the FES were similar
to those of intact neuromuscular system that is performing the same
task, i.e., the muscle activations were designed to clone actual
natural movements. Thus, during the movements the individual could
feel when she was supposed to activate muscle contractions and how
to sequence them to produce desired movements. The fact that marked
changes in the H-reflex were observed and that a number of muscles
that the individual was unable to voluntarily contract prior to the
FES-mediated protocol were under her voluntary control at the end
of the protocol suggests that the functional improvements induced
by the FES-mediated protocol are in part due to changes that occur
in the central nervous system. In other words, the intensive,
repetitive and yet diverse FES-mediated protocol may be promoting
plastic reorganization of the central nervous system. Therefore it
is predicted that the following mechanism may cause the changes
observed. If a hemiplegic individual who strains to execute a task
is assisted with the FES to carry out that same task, he/she is
effectively voluntarily generating the motor command (desire to
move the arm, i.e., efferent motor command) and the FES is
providing the afferent feedbacks (afferent sensory input),
indicating that the command was executed successfully. Therefore,
it is believed that by providing both the motor command and sensory
input to the central nervous system repetitively for prolonged
periods of time, this type of FES-mediated protocol facilitates
functional reorganization and retraining of intact parts of the of
central nervous system and allows them to take over the function of
the damaged part of the central nervous system. As the individual
continues to improve the voluntary function then the
volitional-related sensory feedback from the stimulated muscles and
arm further contributes to this retraining process. This is
possible due to the distributed nature of the central nervous
system and the fact that various parts of the brain are responsible
for processing similar tasks. For example, motor tasks are
typically associated with motor and pre-motor cortex activity.
However, the motor tasks are also processed in the occipital lobe.
Therefore, FES-mediated protocol is allowing the central nervous
system to access such distributed networks and used them to help
patient relearn new motor tasks, lost due to injury or disease of
the central nervous system.
[0198] The present exemplary FES-mediated study may confirm that
the FES-mediated protocol can be used to improve the upper limb
functions in chronic stroke individuals. Furthermore, as this type
of protocol may be effective in individuals with severe upper limb
impairment, it is very likely that it is effective in individuals
with less severe upper limb disability. The exemplary study
investigated on weekly basis how the H-reflex and the EMGs of
various muscles changed over time due to FES-mediated protocol. The
key finding is that the muscles that were paralyzed prior to the
study became active and were under voluntary control of the
individual after the FES-mediated protocol. Furthermore, the
H-reflex decreased almost 50% after the FES-mediated protocol was
completed suggesting a significant reduction in muscle tone and/or
spasticity as a result of this exemplary FES-mediated protocol. It
would be appreciated that example embodiments may be applied to a
variety of pulse generating circuits. For example, some pulse
generating circuits are described in PCT application publication
number WO2011/150502 entitled FUNCTIONAL ELECTRICAL STIMULATION
DEVICE AND SYSTEM, AND USER THEREOF, filed Jun. 2, 2011, having a
common co-inventor as the present application, the contents of
which are hereby incorporated by reference. Such circuits may be
programmed in accordance with at least some of the presently
described example embodiments.
[0199] Some example embodiments may be applied to a "matrix-type
electrode" as would be understood in the art. For example, a single
output channel can be used to stimulate more than one point of
contact on the skin, using a matrix of contact points. These points
can be programmed or controlled in a number of ways, as
appropriate.
[0200] It would be appreciated that the described FES systems may
differ from some traditional fixed voltage systems which do not
consider any desired steady state current value. Further, the
described FES systems may differ from traditional current
controlled systems which attempt to generate a rectangular current
pulse, or attempt to dampen the current spike, or may merely
measure the current until a total charge desired is reached.
[0201] Another example application of at least some example
embodiments is for the rehabilitating, treating, retraining, and/or
otherwise improving upper extremity mobility and control in persons
having impaired or disabled upper extremities due to stroke or
spinal cord injury, including stimulation of the lumbricalis
muscles. An example of such a system and method is described in PCT
application publication number WO 2014/000107 filed Jun. 26, 2013,
having a common co-inventor as the present application, the
contents of which are hereby incorporated by reference.
[0202] At least one example embodiment recognizes that there can be
biological cross-talk between electrode leads in close proximity,
such as when stimulating a group of close muscles such as the
lumbricalis muscles. For example, if a spike in current of one
electrode lead causes biological cross talk during the steady state
current of another one of the electrode leads, this can affect the
measurement of the signal levels which are taken during the steady
state current of the another one of the electrode leads.
[0203] In an example embodiment, there is provided electrical
stimulation system for providing pulse stimulation to a plurality
of areas of a living body by way of a plurality of electrode leads
each applied to one of the respective areas, each of the areas
including an associated resistance element and an associated
capacitance element. The system includes a plurality of pulse
generating circuits each having a controllable output voltage to
generate constant voltage pulses to one or more of the electrode
leads, wherein the corresponding current signal of each constant
voltage pulse includes an exponential decay to a steady state
current value. At least one controller is configured to determine a
specified target steady state current value to be applied to each
area, estimate the associated resistance element of each area,
control the pulse generating circuits to generate a constant
voltage pulse to the electrode leads at a calculated voltage level
which achieves the specified steady state current value to the
area, and control a spike of one of the current signals for one of
the electrode leads so as to be outside the steady-state current of
another one of the electrode leads so as to allow accurate
measurement of the steady-state current of the another one of the
electrode leads.
[0204] In another example embodiment, there is provided electrical
stimulation system for providing pulse stimulation to a plurality
of areas of a living body by way of a plurality of electrode leads
each applied to one of the respective areas, each of the areas
including an associated resistance element and an associated
capacitance element. The system includes a plurality of pulse
generating circuits each having a controllable output voltage to
generate constant voltage pulses to one or more of the electrode
leads, wherein the corresponding current signal of each constant
voltage pulse includes an exponential decay to a steady state
current value. At least one controller is configured to estimate
the associated resistance element of each area, control the pulse
generating circuits to generate a constant voltage pulse to the
electrode leads at a specified voltage level based on the measured
steady-state current value, and control a spike of one of the
current signals for one of the electrode leads so as to be outside
the steady-state current of another one of the electrode leads so
as to allow accurate measurement of the steady-state current of the
another one of the electrode leads.
[0205] In an example embodiment, each constant voltage pulse from
the respective pulse generating circuits for all of the electrode
leads is controlled to pulse simultaneously (e.g. rise time
starting position is substantially the same). In another example
embodiment, the controller controls a spike of one of the current
signals for one of the electrode leads so as to be within the
exponential decay of another one of the electrode leads, so long as
the spike is within a buffered time before the steady state of the
another one of the electrode leads. This type of system contrasts
with having to fire each pulse one-by-one, for example.
[0206] In an example embodiment, at least some of the plurality of
areas are relatively located at a distance there between so as to
cause biological cross-talk between two of the respective areas of
the body where the respective electrode leads are located.
[0207] In an example embodiment, to reduce or eliminate the effects
of biological cross-talk the current spike to at least one of the
electrodes is controlled by applying a phase control, a delay
control, or a compensating circuit, to at least one of the current
signals for the respective electrode lead. Adjustment and
calibration of each of the pulse generators in this manner may be
performed prior to starting the present treatment protocol.
[0208] At least some example embodiments can be applied to other
electrical stimulation systems. For example, a pacemaker or
defibrillator may be configured to provide electrical stimulation
to the heart in a controlled manner. Other example electrical
stimulation system can be applied to neural stimulation for the
brain, to assist in facilitating neural pathways, for example. Such
a system, when configured with the electrical stimulation systems
described herein, may include a controller configured to determine
a specified target steady state current value to be applied to the
area, and control the pulse generating circuit to generate a
constant voltage pulse to the one or more electrode leads at a
calculated voltage level which achieves the specified target steady
state current value to the area. Each generated constant voltage
pulse can include a faster rise time resulting in a lower required
specified target steady state current than when compared to a
constant voltage pulse having a slower rise time requiring a higher
required specified target steady state current. This, for example,
can save the amount of power consumed or total energy required to
be provided by the source (e.g. limited lifetime battery). In
another example embodiment, at least one electrode lead, and/or a
portable battery, are implanted inside of the patient. Accordingly,
reduction of power consumption can lead to improved patient
comfort, longer use of the battery, and less surgery time required
for replacing of the battery.
[0209] The example embodiments use constant voltage pulses which
are in contrast to, and not the same as, a pulse generator which
generates a rectangular constant current pulse. In a constant
current pulse system, the current does eventually reach a desired
steady state current value, but such systems can suffer from slow
rise times due to the capacitance of the skin and other elements,
for example. Also, such conventional systems do not have an initial
inrush of current and can require a higher steady state current
value when compared to the systems as described in at least some
example embodiments.
[0210] While some of the embodiments are described in terms of
methods, a person of ordinary skill in the art will understand that
present embodiments are also directed to various apparatus
including components for performing at least some of the aspects
and features of the described methods, be it by way of hardware
components, software or any combination of the two, or in any other
manner. Moreover, an article of manufacture for use with the
apparatus, such as a pre-recorded storage device or other similar
non-transitory computer readable medium including program
instructions recorded thereon, or a computer data signal carrying
computer readable program instructions may direct an apparatus to
facilitate the practice of the described methods. It is understood
that such apparatus, articles of manufacture, and computer data
signals also come within the scope of the present embodiments.
[0211] While some of the above examples have been described as
occurring in a particular order, it will be appreciated to persons
skilled in the art that some of the steps or processes may be
performed in a different order provided that the result of the
changed order of any given step will not prevent or impair the
occurrence of subsequent steps. Furthermore, some of the steps
described above may be removed or combined in other embodiments,
and some of the steps described above may be separated into a
number of sub-steps in other embodiments. Even further, some or all
of the steps of the method may be repeated, as necessary. Elements
described as methods or steps similarly apply to systems or
subcomponents, and vice-versa.
[0212] The term "computer readable medium" as used herein includes
any medium which can store instructions, program steps, or the
like, for use by or execution by a computer or other computing
device including, but not limited to: magnetic media, such as a
diskette, a disk drive, a magnetic drum, a magneto-optical disk, a
magnetic tape, a magnetic core memory, or the like; electronic
storage, such as a random access memory (RAM) of any type including
static RAM, dynamic RAM, synchronous dynamic RAM (SDRAM), a
read-only memory (ROM), a programmable-read-only memory of any type
including PROM, EPROM, EEPROM, FLASH, EAROM, a so-called "solid
state disk", other electronic storage of any type including a
charge-coupled device (CCD), or magnetic bubble memory, a portable
electronic data-carrying card of any type including COMPACT FLASH,
SECURE DIGITAL (SD-CARD), MEMORY STICK, and the like; and optical
media such as a Compact Disc (CD), Digital Versatile Disc (DVD) or
BLU-RAY Disc.
[0213] It should be understood that the disclosure is not limited
in its application to the details of construction and the
arrangement of components set forth in the following description or
illustrated in the drawings. The disclosure is capable of other
embodiments and of being practiced or of being carried out in
various ways. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," or "having" and variations thereof herein is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. Unless limited otherwise, the terms
"connected," "coupled," and "mounted," and variations thereof
herein are used broadly and encompass direct and indirect
connections, couplings, and mountings. In addition, the terms
"connected" and "coupled" and variations thereof are not restricted
to physical or mechanical or electrical connections or couplings.
Furthermore, the specific mechanical or electrical configurations
illustrated in the drawings are intended to exemplify embodiments
of the disclosure. However, other alternative mechanical or
electrical configurations are possible which are considered to be
within the teachings of the present disclosure. Furthermore, unless
otherwise indicated, the term "or" is to be considered
inclusive.
[0214] Variations may be made to some example embodiments, which
may include combinations and sub-combinations of any of the above.
The various embodiments presented above are merely examples and are
in no way meant to limit the scope of this disclosure. Variations
of the innovations described herein will be apparent to persons of
ordinary skill in the art having the benefit of the present
disclosure, such variations being within the intended scope of the
present disclosure. In particular, features from one or more of the
above-described embodiments may be selected to create alternative
embodiments comprised of a sub-combination of features which may
not be explicitly described above. In addition, features from one
or more of the above-described embodiments may be selected and
combined to create alternative embodiments comprised of a
combination of features which may not be explicitly described
above. Features suitable for such combinations and sub-combinations
would be readily apparent to persons skilled in the art upon review
of the present disclosure as a whole.
* * * * *